有下面两种方未能可制得白色Fe(OH)2沉淀。 方法一:用不含Fe3+的FeSO4溶液与不含O2的蒸馏水配制的NaOH溶液反应制备。 (1)用硫酸亚铁晶体配制上述FeSO4溶液还需加入 。 (2)除去蒸馏水中溶液的O2常采用 的方法。 (3)生成白色Fe(OH)2沉淀的操作是用长滴管吸取不含O2的NaOH溶液,插入FeSO4液面下,再挤出NaOH溶液,这样操作的理由是 John
has put on so much weight recently that his mother has to ________ all his
trousers to his measure.
A.
let out B.
give away C.
bring in D.
make up