My sister has some trouble ______spelling some of the words in American English, while I have some difficulty ________ my pronunciation.
____ he works hard, I don’t mind when he finishes the experiment.
____, he does not know the answer.
We were ____ to go out for a camp ____ it began to rain.
____ several times, the young scientist still kept on doing his experiments.
It was last October ____ they finally came back to their hometown.