.When he was young, he used to __________ hard at his lessons.
Being young means having all kinds of possibilities, so you should challenge your limits and go ______ your boundaries.
My sister was against my suggestion while my brother was _____it.
To improve your reading ability, you should ____ half an hour every day for learning new vocabulary.
Though he had tried to climb to the top of the mountain several times, he didn't _____.
The good thing about children is that they _____ very easily to new environments.