special help with science questions?

1. For a covalent bond to be considered polar...

a. an electron must be transferred from one element to another.
b. the electrons in the bond must be shared equally.
c. one atom's pull on the electron/s must be greater than the other's pull.
d. both atoms in the molecule must be isotopes.

2. All of the following are Earth's natural power sources EXCEPT..

a. radiation from radioisotopes
b. geothermal energy
c. solar radiation
d. kinetic energy in bouncing balls

3. Which one of the following is NOT characteristic of hydrothermal vents?

a. Entire communities thrive in high temperature and pressure.
b. Abundant sunlight makes possible photosynthesis.
c. Giant tubworms survive because of bacteria that produce food from hydrogen sulfide
d. Spouts of hot, mineral rich water come from the ocean floor

4. Chlorophyll is a light-absorbing pigment which makes possible the ___ of photosynthesis during which ___ is split.

a. Calvin cycle, chloroplasts
b. chemosynthetic reactions, hydrogen sulfide
c. light reaction, water
d. krebs cycle, sugar