A:at, in
B:in, at
C:at, at
—Long time no see.How are things going?
—________,thanks.
与30°W经线构成经线圈的是( )
18世纪六七十年代,新式棉纺织机在英国出现,传统的动力已不适应新的需要,蒸汽机应运而生。这表明( )