是doing。
stick to (doing) sth.坚持(做)某事，此处的to为介词，后面接名词或动名词。
“stick”的搭配和用法
一、 stick to 坚持，信守，紧跟，沿着。
1、stick to one’s guns
固执己见
2、Stick to your colors.
坚持你的观点。
3、Young people should not stick to old ideas and must have the courage to innovate.
年轻人不应该拘于旧说, 要勇于创新。
二、.stick out 突出，显眼；坚持到底
1、If you dress like a tourist, you stick out as a mark for scams at the market.
如果你穿得像个游客，在市场里就会成被骗的目标。
2、stick it out 坚持下去 。
扩展资料：
stick ，英 [stɪk] 美 [stɪk]
它的基本意思是“粘贴”、“张贴”,指用胶水、糨糊、黏结剂等粘贴,也可指一个人或一个物体依附于另一个或两者互相依存,引申还可表示“卡住”“困住”。stick还可作“插入”“刺入”解,指用尖物插入、刺、戳、贯穿。
1、意思“粘贴”、“张贴”用法，to attach something to something else using a substance, or to become attached to a surface
例如：This stamp won’t stick properly. 这张邮票贴不牢。
stick sth on/to/in etc sth
例如：
Someone had stuck posters all over the walls. 有人把海报贴满了墙。
I could feel my shirt sticking to my back. 我能感觉到衬衫贴在了背上。
The oil keeps the pasta from sticking together. 油可避免意大利面粘在一起。
2、意思“插进、刺、戳、插”用法：[I,T always + adv/prep] ，if a pointed object sticks into something, or if you stick it there, it is pushed into it
The boy stuck his finger up his nose. 小男孩把手指塞到鼻孔里。
stick (sth) in/into/through sth
例如：pins stuck in a notice board 插在布告板上的大头针