Thecountryhasalreadysentupthreeunmannedspacecrafts，them...

問題詳情：

The country has already sent up three unmanned spacecrafts，the most recent ________at the end of last March.

A．has been launched              B．having been launched

C．being launched                 D．to be launched

【回答】

B

知識點：非謂語動詞

題型：選擇題