Pitchers threw at his head. is the correct answer because through/threw are homophones which sound alike but have different meanings and different spellings. Through means in one side and out the other. Threw is the past tense of throw. So the correct answer would be "C"
This line "Pitchers through at his head." uses the incorrect "through". This "through" means to go in and out of something, like a doorway. I walked through the doorway into the other room. The sentence needs the "threw" that means to take an object with your hand and propel it to another location. Threw is the past tense of the word throw. It is an irregular past tense verb, so it doesn't follow the rule of adding /ed/ to create past tense.
