he told us whether（ ）a picnic was still under discussion.A having B to have 为什么呢?不是用ing

he told us whether（ ）a picnic was still under discussion.A having B to have 为什么呢?不是用ing
he told us whether（ ）a picnic was still under discussion.
A having
B to have
为什么呢?不是用ing

he told us whether（ ）a picnic was still under discussion.A having B to have 为什么呢?不是用ing
英语中有 疑问词 + to do 做主语或宾语的习惯
比如I really don't know how to answer him.我真的不知道该怎么回答他.
Where to find the key is still a problem.去哪儿找那钥匙仍然是个问题.
楼主问的“用ing 做主语”则是另一码事,在没有疑问词的情况下,to do 和doing 都可以做主语,前者偏向将做的事,后者侧重正做或已做的事.区分不明显的时候,两者可以互换.

因为
1.“whether +to 不定式结构”是固定用法
2.在主句中，“whether to have a picnic was still under discussion”做tell的宾语
3.在whether引导的宾语从句中，whether to have a picnic又做从句的主语

做主语的话ing和不定式都可以啊!
这里有将来的意思 不定式是表示将来 ing表示进行啊.