The half-life of a reaction is time needed to consume half the reactant.

---What time do you expect me back, Mum? ---_____half an hour.

He didi it in _____ time it took me. A: one-third the B: the double C: the one-third D: half a

Half of the time the participants tried to match the target face to another picture of a face with a similar _________ (表情).

杀青 A: completing creation B: killing livestock C: tread on the lawn D: half time

‎杀青‏ A: completing creation B: killing livestock C: tread on the lawn D: half time

half an hour, my parents, back to the hotel, finally find their way (It took sb. time to do …)

The skilled mechanic did it in ______________________time it took me. A: the double B: the one-third C: one-third the D: half a

Which time signal does not appear in the text? （ ） A: in several months B: when the final day came C: a year and half later D: a long, long time ago

When invited to an American partner’s home, you’d better arrive( ). A: 5-10 minutes after the scheduled time B: on time C: 5-10 minutes before the scheduled D: Half an hour after the scheduled time