她表面上说是去图书馆学习，实际上却是和朋友去逛街。

She ostensibly went to the library to study, but actually went shopping with friends.

ostensibly 是副词，由形容词 ostensible（表面的、假装的）加上副词后缀 -ly 构成。这个词表示"表面上、看似"，暗示实际情况可能与表面宣称的不同。