分析如下：
1. if you were asked, “what is the difference between plants and animals?” what
answer do you think you would give?
这个主从句都采用了虚拟语气,只是里面的直接引语“what is the difference between plants and animals?”不是虚拟语气.
2. Your first thought might be that a plant has leaves and roots and flowers,
此句中的从句that a plant has leaves and roots and flowers不是虚拟语气,想必也不用解释.
主句Your first thought might be...可以视为是虚拟语气,因为它也可以视为是对上句的回答,省略了if...从句.
即：Your first thought might be that a plant has leaves and roots and flowers,
= If you were asked, “what is the difference between plants and animals?”, your first thought might be that a plant has leaves and roots and flowers,
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