What does it mean that the two strands of dna are complementary?

Weights of golden retriever dogs are normally distributed. samples of weights of golden retriever dogs, each of size nequals15, are randomly collected and the sample means are found. is it correct to conclude that the sample means cannot be treated as being from a normal distribution because the sample size is too small? explain.

Galaxy whose shape seems different follow no set pattern are classified as

What must be true for natural selection to heppen