No words are strong enough to express our thanks foryour help.— _____.

下列句中加点词语古今意思全相同的一项是（ ）

I called you last night, but nobody answered.—Oh, I usually___off my cellphone by 9:00 p.m

r their help, we ____ the program intime

I won’t tell the student the answer to the math problem until he______ on it for more than an hour.