题目选项分析

Unable to build nests or care for their young, female cowbirds lay up to 40 eggs a year in the nests of other birds, including warblers, vireos, flycatchers, and thrushes.

Unable to build nests or care for their young, a female cowbird will use the nests of other birds to lay up to 40 eggs a year, including those of warblers, vireos, flycatchers, and thrushes.