Which do you enjoy _to spend_your spare time__（度过你的空闲时间）, playing cards at home or taking a walk in the park?
可以理解正确答案是：不定式做目的状语。但为何不能填spending 呢？
You enjoy spending your spare time in playing cards at home ortaking a walk in the park.如此不可以么？
Which do you enjoy to spend your spare time, playing cards at home or taking a walk in the park?
—— 这个句子错误百出，不可思议。
改为：
Which do you enjoy spending your spare time in, playing cards at home or taking a walk in the park?
【注】which 表示选择，指：playing cards at home or taking a walk in the park，需要加介词 in，需要做句子成分，不然被架空。
【答语】
（1）I enjoy spending my spare time in playing cards at home
（2）Ienjoy spending my spare time in taking a walk in the park.
所以，网友这个句子没错。
You enjoy spending your spare time in playing cards at home ortaking a walk in the park.