如图是一对夫妇的体细胞染色体组成图，请分析回答：

氢气是一种高能燃料，实验室在点燃氢气之前必须检验纯度，检验方法为：____ 反应方程式为：　____ ，其中水中氢元素的化合价为　____ 　，生活中常用____ 的方法将硬水变为软水．

    Where do you want to send your boys to study?A mixed school or a boys' school?____ (traditional),boys and girls attend a mixed school,where they study together.But boys in a single-sex school____(say) to be more likely to get involved in____(culture) and artistic activities that help develop their emotional expressiveness than____(teach) alongside girls,according to the findings of some researchers.

    They say in a single-sex school teachers can tailor lessons to boys' learning style,____they can also encourage boys to enjoy reading and writing with "boy-focused"____(approach) that appeal to them.For example,they are more active and can learn best through touch,so letting them move around____classroom and getting them____(compete) in teams can prevent boredom.“What's more,boys in a single-sex school won't feel forced to act____men before they understand____(them) well enough to know what that means.”the study reported.

下列各句中，划线的成语使用恰当的一项是（   ）