A:-824.4kJ·mol-1
B:-627.6kJ·mol-1
C:-744.7kJ·mol-1
D:-169.4kJ·mol-1
R
X
Y
Z
My father was reading a book ________ I was doing my homework.
.如图,把矩形ABCD沿EF对折后使两部分重合,若∠1=50°,则∠AEF=____ 。