颜面部修复手术在瘢痕的早期充血阶段进行，不仅_________，同时术后会产生_____________。
参考答案：手术时出血多；更多的增殖性瘢痕
设F是属性组U上的一组函数依赖，下列叙述正确的是
A．若Y
X，则X→Y为F所逻辑蕴含
B．若X
U，则X→Y为F所逻辑蕴含
C．若X→Y为F所逻辑蕴含，且Z
U，则X→YZ为F所逻辑蕴含
D．若X→Y及Y→Z为F所逻辑蕴含，则X→Z为F所逻辑蕴含
—What were you doing when I rang you this morning?
—I was occupied ______ the housework and kept my son occupied______ his homework.
A．at；doing
B．with；doing
C．at；to do
D．with；to do
X，则X→Y为F所逻辑蕴含
U，则X→Y为F所逻辑蕴含
U，则X→YZ为F所逻辑蕴含