How do algae help keep the balance of an aquatic ecosystem? Select all that apply. 1.by releasing oxygen
2.by providing food for consumers
3.by absorbing carbon dioxide
4. by releasing carbon dioxide

more info ? ? i don't understand what the question is

explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.