Question

Don’t talk about such things of _ you are not sure .A that B which C WHAT D WHO详细解释

Answer 1

选B。 定语从句固定搭配
be
sure
of
sth
的介词of
少宾语，所以用关系代词which指代事物，先行词是things，of
which引导定语从句
注意：as、that、who三个关系代词不能跟在结构之后，作介词宾语

Answer 2

选择B，which，因为
of
是介词，而且此句为定语从句，先行词为things，定语从句中介词后一般接which