小林家里新买了几件电器后,发现家中的保险丝经常熔断,原因可能是( )
A:电阻过大
B:灯丝烧断
C:用电器总功率过大
D:电压太大
你会做下列加法题吗?
①What's six and one? It's ____.
②What's two and three? It's ____.
③What's zero and nine? It's____.
④What's four and three? It's____.
⑤What's one and five? It's____.
1958年,美国科学家斯图尔德用胡萝卜韧皮部细胞培养出完整的胡萝卜植株。该过程不需要( )