How would you use a completely randomized experiment in each of the following settings? Is a placebo being used or not? Be specific and give details.

(a) A veterinarian wants to test a strain of antibiotic on calves to determine their resistance to common infection. In a pasture are 22 newborn calves. There is enough vaccine for 10 calves. However, blood tests to determine resistance to infection can be done on all calves. (Select all that apply.)

A. Use random selection to pick 5 calves to inoculate.
B. No placebo is being used.
C. After inoculation, test 5 calves to see if there is a difference in resistance to infection between the two groups.
D. After inoculation, test 10 calves to see if there is a difference in resistance to infection between the two groups. Use random selection to pick 10 calves to inoculate.
E. A placebo is used for the remaining 12 calves.
F. After inoculation, test all calves to see if there is a difference in resistance to infection between the two groups.