BY THE TIME A BABY HAS REACHED HIS FIRST BIRTHDAY, HE SHOULD _____...

19. - ON TAP HK II TRAC NGHIEM LOP 11
ON TAP HK II TRAC NGHIEM LOP 11

19.

By the time a baby has reached his first birthday, he should ________sit up or even stand up.

A. to be able to

B. able to

C. to be able

D. be able to