請回答第 46 題至第 50 題
Twitter is a social network that allows users to send and 46________ short messages, called tweets. Tweets
can be 47________ 140 characters long. You can post an upcoming event, organize group conversations or just tell
the world 48________ you are at the moment. Twitter has become very 49________ . Since its birth in 2006 ever one
hundred million people around the world 50________ it regularly.
【題組】50
(A)use
(B)used
(C)have been using
(D)had used