B. GROUP BY is used to group aggregates. The other clauses are all valid but do not group data, which is required here.
A2:
D. WHERE and ORDER BY are not required, and neither is an alias (although an alias should ideally be used). The HAVING clause, however, must contain entries from the SELECT list.
A3:
B and D. The average function is AVG, and the function used to total values is SUM.
