1. Tourism was then still in its infant stage.
    旅游业当时还处在初创阶段。

2. He was holding an infant in his arms.
    他抱着婴儿.

3. "Mom" is not right, because the woman or women who supplied the egg and gave birth to the infant would more appropriately be called Mother.
    称呼"妈妈"不正确，因为提供卵子并生下婴孩的女子才更有资格被称为母亲。