It is ____ asking Tom for help, for he is always the last to help others.
| A．useful | B．helpless | C．helpful | D．useless |
The little boy was so careless with his spelling that he often ________ letters from words.
| A．left out | B．left behind |
| C．left off | D．let alone |
Evidence obtained from observation and experiment is often used to ________ a scientific theory.
| A．confirm | B．claim |
| C．conclude | D．calculate |
．Faced with a problem，you have to ________ it first，and then try to find a solution.
| A．resemble | B．substitute |
| C．concentrate | D．analyze |
Teaching pronunciation class to a mixed group of learners can ________ a teacher with many challenging problems.
| A．provide | B．produce |
| C．present | D．offer |
All my pockets have been ________ but I can’t find my keys.
| A．got through | B．given out |
| C．gone through | D．gone down |