Let's cancel out our options to find the correct answer. Drowning is basically someone who can't breath, so clammy skin is out; asthma is someone who also cannot breath well alongside chest constrictions, but that has nothing to do with clammy skin again; head injuries only affect the head, so it should not change the way your skin looks, which leaves us with shock. And it just so happens to be that shock is the correct answer. A little google research never hurt anyone! :)
