One of my friends studies art 为什么这里的study是studies?

One of my friends studies art 为什么这里的study是studies? My friend,Marry,___maths well 这里是studies还是study?急 Studies pass into and influence manners 是Of Study原文里备注的吗?还是大 study的三单形式为什么是studies,那不就成复数了吗? One of the most interesting of all studies is the study of w study复数是studys 还是studies He____(study) English very hard!答案为什么是studies,而不是does study? Both of my parents( )my studies .is good for our studies study在这里是什么意思 He often helps me study English.中的study为什么不是单三特有形式的studies? in the school she studies hard为什么是studies My sister studies hard .为什么不用hardly