及物动词后直接加名词如see,I see a bird.而不及物动词后面要加介词再接名词.
也就是： 及物动词+名词 ； 不及物动词+介词+名词
across是介词,cross是动词 go across=cross
think of 1.是考虑某事物如You can't expect me to think of everything!
2.考虑某事的可能性 I'm thinking of travelling abroad.
3.想起 Spring makes me think of beautiful flowers.
think about 考虑I will think about it if I have time.