Identify the following as either matched pair or independent samples. Also identify the experimental units, treatments, and response in each case.
(a) Twelve persons are given a high-potency vitamin C capsule once a day. Another twelve do not take extra vitamin C. Investigators record the number of colds in 5 winter months.
(b) One self-fertilized plant and one cross-fertilized plant are grown in each of 7 pots. Their heights are measured after 3 months.
(c) Ten newly married couples are interviewed. Both the husband and wife respond to the question, "How many children would you like to have?"
(d) Learning times are recorded for 5 dogs trained by a reward method and 3 dogs trained by a reward-punishment method.