ascertains

英[ˌæsəˈteinz]

v. 弄清, 确定, 查明( ascertain的第三人称单数 )

v establish after a calculation, investigation, experiment, survey, or study\nv be careful or certain to do something; make certain of something\nv find out, learn, or determine with certainty, usually by making an inquiry or other effort\nv learn or discover with certainty