—Guang'an is a beautiful city, isn't it?
—Yes. There are about two _______ visitors here every week.
A:thousands of
B:thousands
C:thousand
D:/
低钠盐适合患有高血压、肾病、心脏病的患者服用,苹果酸钠盐(C4H5O5Na)是低钠盐的一种。请回答:①苹果酸钠盐的相对分子质量是____。②苹果酸钠盐中氢和氧元素质量的最简质量比为____。
二五____
二八____
二____得八
二六____