下列关于四类微生物的叙述，不正确的是（  ）

2016年二十国集团（G20）领导人峰会已在中国杭州举办。下面是这次峰会的会标，请写出构图要素，并分别说明其寓意，要求语意简明，句子通顺，不超过80个字。

The Voice of China

    Many Chinese like watching The Voice of China, because the songs sound really good. My daughter, my wife and I like it, too. We watch the programme(节目) every Friday. Some famous singers like Wang Feng, Zhang Huimei, Na Ying, Harlem Yu are the coaches. The coaches listen to the songs, and find their favorite singers. They can listen to the singers , but they can't watch the singers sing . Then they teach (教) their favorite singers. The singers sing songs again. The Voice of China is to find the best voice.

若x=2是方程ax-3=x+1的解，那么a等于                         （   ）