To better enjoy the benefit of free flow of goods, services, capital, labor and other resources，countries have signed various agreements to liberalize trade among themselves while possibly ______ barriers to economic activities with non-members.

To better enjoy the benefit of free flow of goods, services, capital, labor and other resources，countries have signed various agreements to liberalize trade among themselves while possibly ______ barriers to economic activities with non-members.

A.putting up

B.put up

C.putted up

D.following up

正确答案是A