The correct answer is A. -er
Step-by-step explanation:
In language, a suffix is a letter or set of letters called affix that is added after a basic word which gives meaning to the word and creates a new word derived from the original. In the case of the word "player" that means someone who plays this word derives from a Middle English word and it is composed by the root or basic word "play" which is performing or doing an activity for recreation and the suffix "-er" that is used to form nouns from verbs and means "the one who" as in cooker "the one who cooks" or player "the one who plays". Therefore, the suffix of the word player or the affix added t the root word "play" to form a new word is "-er".