Estuaries are productive ecosystems because they constantly receive nutrients from... A rivers and oceans
B. coral reefs
C. lakes and ponds
D. photosynthesis

answer: 21

step-by-step explanation:

divide 630 by 30. 30 goes into 630 21 times

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

burning fossil fouls really decrease the carbon in the atmosphere so b