21. I can’t carry the box _____ my own; it’s too heavy.
A. of B. on C. for D. to
22. My computer began to return to the _____ running state after I killed the virus by newly-updated Kill 3000.
A. ordinary B. normal C. usual D. common
23. We are _____ water. We’d better store some.
A. running out of B. running out C. run out D. run out of
