Just as the value of a telephone network increases with each new phone ________ to the system, so does the value of a puter system increase with each program that turns out．
A.adding
B.to have added
C.to add
D.added
网友回答
D解析A、B、C、D四个选项的意思都是“增加”．add sth．to sth．意思是“给……增加”，to前缺少宾语；此外，根据with sth．+done 的结构，D项符合题意．