Ireally need with these marine science questions

1: most species of fish require dissolved oxygen for their metabolism. why would these species tend to be found in shallow ocean zones?

a: there is more gas exchange in shallow ocean zones.
b: there is lower temperature in shallow ocean zones.
c: there is less pressure in shallow ocean zones.
d: there is less gas exchange at shallow ocean zones.

2: cyanobacteria are organisms that use the sun's energy to produce their own food. during a storm, a population of cyanobacteria was carried down into a deeper layer of the ocean. predict what would happen to this population.

a: it would thrive, because water currents would carry it farther from the shore.
b: it would thrive, because more nutrients are available deeper in the ocean.
c: it would die, because sunlight is unable to penetrate deep into the ocean.
d: it would die, because oxygen levels are higher in deep zones of the ocean.

3: a marine scientist observes that dissolved oxygen decreases with increasing ocean depth. he concludes that deep sea creatures must require less oxygen than those at shallower depths. why is this an invalid scientific conclusion?

a: the data he collected were not compared to those collected at other sites.
b: the data he collected was inaccurate.
c: the data he collected was from a laboratory and not in natural conditions.
d: the data he collected was relative and not absolute.

4: how does the density of solid water (ice) affect aquatic life?

a: it allows ice to float to the top of water, allowing life to live below.
b: it allows ice to sink to the bottom of water, allowing life to live above.
c: it traps air within solid ice, allowing life to breathe within air pockets.
d: it produces bubbles as it freezes, allowing life to breathe under water.