问题补充:
In those days ,books could only be produced one at a time .
A. in hand
B. with hand
C. by hand
D. by hands
答案:
A. in hand
B. with hand
(答案→)C. by hand
D. by hands
解析:in hand在手头,在控制中;with hand用手;by hand用手,手工的;by hands无此说法。句意:在哪个时代,书籍只能手工一本一本地写。With一般表示用某种工具,by表示用某种方式,结合语境可知本句中强调书籍的生产方式,故选C。