清凉甘甜的汽水中常含柠檬酸，已知柠檬酸的化学式为C6H8O7，请回答： （1）柠檬酸中碳、氢、氧三种元素的原子个数是_________． （2）柠檬酸中碳元素
用高速离心法打破叶绿体膜后，类囊体薄膜和基质都释放出来。在缺二氧化碳的条件下，给予光照，然后再用离心法去掉类囊体薄膜。黑暗条件下，在
The Day of the Dead, an ancient Mexican festival, is not a sad day, but time to celebrate cycle of life. A．a, the B．不填, the C．不填,
以16m/s的速度水平抛出一石子，石子落地时速度方向与抛出时速度方向成370，不计空气阻力，那么石子落地时的速度是多大？石子抛出点与落地点的高度
Number sense is not the ability to count. It is the ability to recognize a 14 in number. Human beings are born with this ability. 15 , experiments show that many animals are, too. F
若复数(a－1)(a－3)＋(a－1)i是纯虚数，则实数a的值为( ) A． 3 B． 1 C． 1或3 D． －1
—How do you like the football match? —Wonderful，I believe. Just as fine as ________ of the matches we’ve ever seen. A．one B．another C．some
1 mol 下列固体物质①Na2O ②NaOH ③Na2O2 ④Na2SO3长期放置在空气中，固体质量增加的关系(不考虑潮解因素)正确的是A.①=②＞③＞④
