although it's not easy to tell_______ it's good or bad.a if b.whether

although it's not easy to tell_______ it's good or bad.a if b.whether
although it's not easy to tell_______ it's good or bad.
a if b.whether

although it's not easy to tell_______ it's good or bad.a if b.whether
这不是一个句子吧,后面应该还有的.
就这里而言,应该用whether,因为后面有or bad.whether... or...是……或……
I don't know whether it is good or bad.

按照我们的习惯，都是用whether;但是经过查证，if也是可以用的。只不过我们还是选择更为常用的短语更无可厚非。

whether