He decided on blue rather than green.他选定了蓝色，没选绿色。

We looked at all the cats in the pet store and finally decided on a little black-and-white one.我们看了宠物店里所有的猫，最后选定一只黑白相间的小猫。

I am having trouble deciding on a gift for them.我拿不定主意送他们一件什么礼物。