ANSWER IS C
C. The joining of an egg and a sperm
Explanation:
Fertilisation
is the fusion of haploid gametes, egg and sperm, to form the diploid zygote. Note though there can be subtle differences in the fertilization process which occurs naturally within the body or through reproductive technologies outside the body, the overall product in both cases is a diplod zygote
It is D, sharing appreciation for what is being said. Both A and B aren't crucial to being a good listener, in fact in practice they effectively draw attention to yourself, which would be fine if the question was regarding being a good conversationalist. Additionally, C is just completely irrelevant, that wouldn't even be a good conversation practice, let alone a trait important to listening.
Answer: Those parts is were all the oxygen is distributed through the human body, and so technically it can be considered the respiratory system.
The second sentence would be the correct replacement for the sentence