1.introduce a sufficient condition: if/when/whenever/every/all/any/people who/in order to/to

2.introduce a necessary condition: then/only/only if/must/require/no,none(在句子开头)

3.unless equation: unless/except/until/without(其后面部分变成必要条件，其它加NOT变充分条件)

4.特例：the only way to achieve success is to work hard. achieve success(充分条件)

only a professional consultant can solve the organization’s problems. a professional consultant(必要条件)

no citizen can be denied the right to vote. denied the right to vote(充分条件). no citizen(必要条件)

好贴。

"no citizen can be denied the right to vote. denied the right to vote(充分条件). no citizen(必要条件)"

??? 不懂。

I would say "citizen" is a sufficient condition for "right to vote".