If you are uncertain about your physical condition, check with your doctor before trying these exercises.如果你对自己的身体状况不是很确定，尝试这些锻炼之前先咨询一下你的医生。Two candidates for the job seem very good, and three others are borderline. 候选人中有两名似乎很适合这份工作，但另外三名则不是很确定。Early in life she was convinced she wanted to be a composer.早年的时候，她很确定自己想成为一名作曲家。