( )21. Peng Liyuan, _______ first Lady of China invited Obama’s wife and his children to visit China ________ March, 2014.
A. a, on B. the, in C. a, in D. the, on
( )22. My father’s new cell phone can be used _________ e-mails. But he says he isn’t used ________ on such a small screen.
A. to send, to write B. for sending, to write
C. to send, to writing D. to sending, to writing
