一本书打七五折后售价2.5元，这本书的原价是10元．______．
2.5÷75%=313（元）；
313＜10；
故答案为：×．
用佛尔哈德法测定Ag+需要用直接滴定法；测定Cl-时需要用 ① 法，需要加入 ② 以防止沉淀转化。
People can find so many good things, such as useful information and lovely pictures on the web, __________ it is also a global village filled with bad things.
A．what
B．when
C．where
D．while
