Eighteen-four=____
—Oh. Mary's not here these days. Is she ill? —_____.Her mother told me that she was in hospital.
已知： 废钒催化剂中钒元素主要以VOSO4和V2O5形式存在;
V2O5是两性氧化物，不溶于水，溶于酸生成VO2+,溶于碱生成VO3-;
VOSO4是强电解质，溶于水电离出VO2+。
回答下列问题：
