把盛水的纸盒放在火焰上烧,水烧开了,而纸盒不会烧着,这是因为[ ]
A.水把热量传给空气了
B.纸的燃点比水的沸点高
C.火焰的温度低于纸的燃点
D.水能灭火
答案:B
Everything _____ doing is worthy of _____ well.
A.worthy; being done
B.worthy; doing
C.worth; being done
D.worth; doing
原核生物复制过程中起稳定已解开单链作用的是
A.引物酶B.连接酶C.解螺旋酶D.单链DNA结合蛋白