while后面加动词是加动词原形呢?动词的ing形式?

题目

while后面加动词是加动词原形呢?动词的ing形式?
例如:we must elevate our cultural level while (improve/improving)our wealth.

答案

加现在分词例句：She listened to her favourite rock music while singing along with the words.She was putting on her jeans while asking me to hand her the sweater.He banged on the door while opeaning it...