i really want to know how the differences came about为什么是came about

i really want to know how the differences came about为什么是came about
1.I really want to know how the differences came about为什么是came about?句子里没有多余的谓语啊,所以应该用come about啊.而且也没有时态,怎么会这样.
2.Michael sees a foreigner putting out his hand with his thumb raised.为什么是raised,这个我查过了,但是还是看不懂啊,这个意思是伴着他举起的拇指,不及物动词raise不是没有被动语态么,raised不是说他的thumb被举起么!就算有也是be raised吧!
英语教材是这样的,老师仔细解答给我一下哈,毕竟我才是初三嘛.请老师加我为好友,到时候有不懂的问题好直接问您!