LO Which cell structure in the model above indicates that this must be a plant cell?
A The cell wall
B. The cell membrane
C. The nucleus
D. The mitochondria
Please help

Which of the following statements is true? a. elements in the last period are radioactive. b. atomic weight is the same as atomic mass. c. elements in the same group have the same number of electron shells. d. atomic number equals the number of neutrons in the nucleus of an atom.

The volume of helium in a blimp is 6.28 x 10^9 millimeters. the density of helium in the blimp is .1786 kilogram/meter^3. find the mass of the helium in the blimp.

How many grams of oxygen gas are contained in a 15 l sample at 1.02 atm and 28°c? show your work.