My approach:
I) No senator spoke at the convention unless he or she was a
Democrat. => If a senator spoke at the convention, then he or she was a Democrat.
II) No Democrat both spoke at the convention and was a senator.
from I, senator+spoke-> democrat.
from II, democrat -> NO(senator+spoke)
I and II denies each other. If both I and II are true, then no senator can speak.作者: tongxun 时间: 2002-10-4 23:01
spry: What's 文氏图?作者: spry 时间: 2002-10-5 00:06
it is Venn diagram which can be used to show the relationship between sets.
rings a bell? remember we use a circle to show a set..........作者: crackok 时间: 2002-10-5 00:28