Bad habits are easily while good ones are hard to develop.
A. kept up
B. caught up
C. drawn up
D. picked up
网友回答
A. kept up
B. caught up
C. drawn up
(答案→)D. picked up
解析：本题考查动词短语。pick up“拾起；(跌倒后)再爬起来；振作精神；(车/船)在途中搭人/带货；(未经正式介绍)结识朋友；无师自通地学会；(偶然、无意地)学会(语言、技术等)；恢复健康”。