下列说法中正确的是
| A．绿色食品是指不含任何化学物质的食品 |
| B．光导纤维是以二氧化硅为主要原料制成的 |
| C．纳米材料是指由一种被称为“纳米”的新物质制成的材料 |
| D．生物固氮是指植物通过叶面直接吸收空气中的氮气 |
相关试题
It’s high time you had your hair cut ; it’s getting _______ . 
| A．too much long | B．much too long |
C．long too much | D．too long much |
My friend showed me round the town, ______ was very kind of him. 
| A．which | B．that | C．where | D．it |
They use computers to keep the traffic _______ smoothly.
| A．being run | B．run | C．to run | D．running |
If you leave the club, you will not be_____back in .
| A．received | B．admitted | C．turned | D．moved |
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