If he studied a small sample it wouldn't be a representative sample. since he got such a large sample there is a chance most likely all organisms follow the rules of evolution.
Answer:
The two strands are held together by hydrogen bonds between the bases, with adenine forming a base pair with thymine, and cytosine forming a base pair with guanine.
Explanation: hydrogen bonds
Uracil is found in RNA and not DNA. DNA instead has thymine
