HE PUT THE TWO LETTERS INTO THE WRONG ENVELOPES ... MISTAKE.A. ONB...

11. - 0 KI NANG TRAC NGHIEM TRONG CAC KI THI TIENG ANH 3 7712
0 KI NANG TRAC NGHIEM TRONG CAC KI THI TIENG ANH 3 7712

11. He put the two letters into the wrong envelopes ... mistake.

a. on

b. by

c. with

d. in

b