— What are you doing?
— I'm _____ my English book.
A:looking after
B:looking at
C:looking for
D:looking like
酵母菌同时进行有氧呼吸和无氧呼吸,如果二者消耗了等量的葡萄糖,这时吸入的氧气与产生的二氧化碳的分子数之比是( )