下列各项表述不正确的一项是（ ）

The colors on the national flags can be ______ differently in different culture, but they have one thing in common, that is, ______of the colours was carefully chosen.

I often think of my old friend Henry, most of _____ letters I still keep.

Thepictureofthepark________memoriesofourclasstriplastyear

What do you think of the summer camp–Wonderful! It’s the greatest ______ I have ever had.