C.
Biotic mean alive, so we can cut off the first 2 easily. Aquatic birds eat frogs, so that one is safe for now. A decrease in something parasitic usually helps the population, so D is out too. The only one left is C.
Answer:
Explanation: Ctenophores move in water, they have a flapping motion.
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Answer:
A purine always forms a complementary base pair with a pyrimidine.
Explanation:
Purine bases such as Adenine pair specifically with Thymine , a pyrimidine base forming two bonds; just as Guanine pair specifically with Cytosine forming three bonds.
This specific base pairing are complimentary in nature and grants stability to the DNA.
Answer:
70% brain and about 60% of our body is water