The day before yesterday Jill____(borrow)a book from me.
I behaved badly yesterday and I am ____ (羞愧的) now.
已知直线:xtanα-y-3tanβ=0的斜率等于2,在y轴上的截距为1,则tanα+β=( )
为了保护南极的生态环境,到南极考察的科学工作者不仅要把塑料等难降解的垃圾带离南极,还需把粪便等生活垃圾带离南极,这是因为南极( )