I am not sure if she is from Canada.还是I am not sure that she is from Canada.原题 is she from Canada?i'm not sure.合并为一句

I am not sure if she is from Canada.还是I am not sure that she is from Canada.
原题 is she from Canada?i'm not sure.合并为一句

I am not sure if she is from Canada.或者 I am not sure whether she is from Canada or not.

I'm not sure if she is from Canada.

前面那句

都可以，但表达意思略有不同。用if表示我不太确定她是不是来自加拿大，用that的话表示我不太确定她是来自加拿大的（对于她来自加拿大这件事情，我不确定，说不好）

I am not sure if she is from Canada

肯定是用if或者whether也行

that

if.

用that