Frank is my pen pal, he _____________ Sydney, Australia.

You have already tried your best, so you _____worry too much about the exams.

If you have difficulty_______a decision，wearing red_______it easier for you to take action．

(2013·长沙二模)—The research on the new flu virus vaccine is challenging  and demanding.Who do you think can do the job?—________ my students have a try?

 Washington ______ get very hot and sticky in summertime. July and August are usually the warmest months.