Why do sunspots appear as dark spots on the surface of the Sun?

Why are small quantities of chlorofluorocarbons so harmful to the ozone layer? a. the chlorofluorocarbons act like ultraviolet radiation causing large amount of ozone to be produced. b. the chlorine from the chlorofluorocarbons reacts with free molecules of oxygen causing a stop in ozone production c. free oxygen atoms can replace the chlorine in chlorine monoxide, releasing a free atom of chlorine which can then recombine with an oxygen atom in ozone, destroying more ozone. d. chlorofluorocarbons absorb ultraviolet radiation, preventing the formation of ozone select the best answer from the choices provided

Maria wanted to grow a fern in her backyard. acting on a suggestion from a friend, she collected brown dots from the underside of a fern's leaves and then potted them. after a few days, maria saw small fern leaves erupting from the pot. which statement explains this phenomenon? a. the fern transitioned from gametophyte generation to sporophyte generation. b. the fern grew as a result of mitosis. c. the fern transitioned from sporophyte generation to gametophyte generation. d. the fern grew to be genetically identical to its parent plant.

Question 11 which of the following personal health practices should a person follow to reduce the risk of skin cancer? avoid staying outdoors when the sun is strongest. consume antibiotics to prevent bacterial attacks. wash hands frequently to maintain proper hygiene. have a balanced diet and exercise regularly. question 12 a student wants to compare how easily a metal and a plastic spoon of the same temperature can transfer thermal energy. which of the following activities should the student perform? measure the effort required to bend each spoon. place an ice cube on each spoon and record the rate of melting of the cubes. place the spoons at room temperature and record the change in temperature of each. measure the change in weight of the spoons after placing them in the freezer for a few minutes. question 13 the characteristics of certain cell divisions are described in the following table. cell division characteristics characteristic description 1 forms diploid cells 2 creates sex cells, or gametes which type(s) of cell division do the two characteristics represent? both characteristics represent meiosis. both characteristics represent mitosis. characteristic 1 represents meiosis and characteristic 2 represents mitosis. characteristic 1 represents mitosis and characteristic 2 represents meiosis. question 14 which of the following adaptations in wooly mammoths could have best prevented their extinction? shedding of fur darker color of fur growth of an extra layer of fur increase in the thickness of fur question 15 maria and ben are both suffering from a hereditary disease, as described in the following table. description of disease patient description maria blood cells get stuck in blood vessels, causing painful attacks ben hemoglobin is abnormal due to curved shape of red blood cells which disease(s) are maria and ben suffering from? both are suffering from type 1 diabetes. both are suffering from sickle cell anemia. maria is suffering from sickle cell anemia and ben from type 1 diabetes. maria is suffering from type 1 diabetes and ben from sickle cell anemia. question 16 which of the following icons is used to represent a female carrier of a disease? a half-filled circle a half-filled square a completely filled circle a completely filled square question 17 joe sowed seeds of a plant in two different types of soil in separate pots. she added the same amount of fertilizer to the pots. she then placed the pots in the sun and recorded their growth after four days. what is the independent variable in the study? duration of growth amount of fertilizer growth of seeds type of soil question 18 philip has curly hair and his sister has straight hair. which of the following explains why philip and his sister have different hair types? both children received the same hair coding gene from their mother. both children received the same hair coding gene from their father. their mother was exposed to different environments before their births. the children each received different genes from their parents. question 19 which statement is most likely correct about species which cannot adapt? they become extinct. their immunity increases. their population increases. they produce more offspring. question 20 four animals live in the arctic. their characteristics are described in the following table. animal characteristics a long tail b small feet c black fur d white skin which animal is least likely to be captured by its enemies? animal a animal b animal c animal d