a an 名词单复数变化 ,出十小题,就是关于a an 的用法,不可数名词和可数名词,例：this is an arm.急用急用 .
问题描述：
a an 名词单复数变化 ,出十小题,就是关于a an 的用法,不可数名词和可数名词,例：this is an arm.急用
急用 .
答
this is a book.
this is an apple.
that is a desk.
that is an earth.
this is a peach.
this is a board
she took half an hour for jogging.
this is an egg.
this is an orange.
this is a cat.