Unlike the fossil fuels of today, biofuels arerenewable sources, which mean that they will not____ easily.

Those are my __ pens D。

She could speak very good English _____ a very young age.

Rather than ______ on a crowded bus, he always prefers _____ a bicycle.

－It seems that Jacky has nothing to do at the moment.－Let me give him ________to read.