以下有关生物多样性及保护的说法正确的是( )
A:外来物种引入一定会危害生物多样性
B:新物种的诞生只是丰富了物种多样性
C:生物多样性间接使用价值远远大于直接使用价值
D:生物多样性的消失不会对人类自身产生威胁
根据短文内容判断正误。对的写正确,错的写错误。
I have a lot of clothes. They are in my bedroom. Look, my new dress is on the bed. It's red. It's so nice. I like it a lot. My shoes are under the bed. They’re black and white. My jeans are on the chair. They’re blue and old. They're too small now. I want a new pair.
用如图所示的电路,测定一节干电池的电动势和内阻.电池的内阻较小,为了防止在调节滑动变阻器时造成短路,电路中用一个定值电阻R0起保护作用.除电池、开关和导线外,可供使用的实验器材还有:
(a)电流表(量程0.6A、3A);
(b)电压表(量程3V、15V)
(c)定值电阻(阻值1Ω、额定功率5W)
(d)定值电阻(阻值10Ω、额定功率10W)
(e)滑动变阻器(阻值范围0~10Ω、额定电流2A)
(f)滑动变阻器(阻值范围0~100Ω、额定电流1A)