Do remember to be ________. We must avoid any possible risks when doing this dangerous chemical experiment—burns, poisonous gases or cuts from broken tubes.
| A．cautious | B．thoughtful | C．considerate | D．curious |
. Bill is not a fast runner and he doesn't have a chance of winning the marathon, but he will _____ the race even if he finishes last.
| A．keep on | B．keep to | C．stick out | D．stick to |
The store had no more red shoes _____, so Mary chose brown ones instead.
| A．in demand | B．in store | C．in need | D．in stock |
. Don't go too far into the sea, children, or the waves will _____ you off your feet.
| A．flow | B．cut | C．press | D．sweep |
He was _____ by a bee when he was collecting the honey.
| A．scratched | B．pricked | C．stung | D．bitten |
A landing on Mars is within the _____ of current physical theory.
| A．scheme | B．scope | C．scrap | D．scale |