工业酒精中常含有毒物质甲醇（CH₃OH），试计算：

①甲醇的相对分子质量______

②甲醇中氧元素的质量分数是多少？

The nurse is teaching a client who receives nitrates for the relief of chest pain. Which of the following instructions should the nurse emphasize ？（）

A．Repeat the dose of sublingual nitroglycerin every 15 minutes for three doses.

B．Store the drug in a cool, well-lit place.

C．Lie down or sit in a chair for 5 to 10 minutes after taking the drug.

D．Restrict alcohol intake to two drinks per day.