Consider the following premises. For all y, y is a police officer or y is not sad. For all y, y will drink water if and only if y is sad. Can we infer the following from them? For all y, if y drinks water, then y is a police officer.
 From the fact that for all y, y is a police officer or y is not sad we can infer that for all y, if y were sad, then y is a police officer. From the fact that for all y, y will drink water if and only if y is sad we can infer that for all y, if y drinks water, then y is sad. Finally, from the fact that for all y, if y drinks water, then y is sad, and that for all y, if y were sad, then y is a police officer we can infer that for all y, if y drinks water, then y is a police officer. Therefore, the answer is yes.