Answer:
complementary events are always mutually exclusive
Explanation:
Two events are mutually exclusive if they cannot occur at the same time (for example, if a veterinary have dogs and cats, if you pick a random animal it can be a CAT or a DOG, but cannot be both, a catdog...) while two events are said to be complementary when one event occurs if and only if the other does not take place (like a coin, if you have a HEAD its because you DON'T have a TAIL)
So option D: complementary events are always mutually exclusive