----Jack can’t concentrate on his lessons recently.
----Yes, that might _____ his low score in the last test.
A．stand for B．apply for C．account for D．call for
There were two boys in the lab, _______ did the experiment successfully.
A．the clever of whom B．the cleverer of whom
C．the cleverer of them D．the more clever of them
Every boy and every girl as well as some teachers who_____ to visit the museum______ asked to be at the school gate before 6 :00 in the morning.
A．are ; are B．is; is C．is ;are D．are ;is
__________both sides accept the agreement will a lasting peace be established in this region.
A．If only B．Only if C．unless D．As long as
The time he has devoted in the past years _______ the disabled is now considered ________ of great value.
A．to help; being B．to helping; to be C．to help; to be D．to helping; being
As ________ rule, apples are sold by ______ weight and eggs by _______dozen.
A．a; 不填；the B．a; the; the C．a; a; the D．the; 不填；不填
