Friction is the force that one surface exerts on another when they rub together. friction works in the direction opposite to the motion, causing the object to slow down. what is one way you could reduce the friction between two surfaces? a.) carpet the surfaces b.) put oil on the surfaces c.) put sand on the surfaces d.) allow one of the surfaces to rust

Many plants can reproduce asexually. which of these is an example of asexual reproduction in a plant? a. pine cones forming on a tree b. cross-pollination in a tomato c. roots sprouting from a potato d. night-blooming jasmine flowers

The current thought on the structure of the cell membrane is: a. a static phosphate sandwich of lipids b. a fluid-mosaic of phospholipids and proteins c. a bilayer of proteins with static lipid molecules d. an impermeable bilayer of protein molecules e. a static and permeable phospholipid single layer

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?