Only one sperm cell can enter into an egg cell. How do you think the receptor helps with making sure only one enters?

acid rain does not usually kill trees directly. instead, it is more likely to weaken the trees by damaging their leaves, limiting the nutrients available to them, or poisoning them with toxic substances slowly released from the soil. the main atmospheric pollutants that affect trees are nitrates and sulphates.

the answer is a! (2.9 x 10^-18 j) hope i could someone. : )