John Gill Commentary Mark 11:33

"And they answered Jesus and say, We know not. And Jesus saith unto them, Neither tell I you by what authority I do these things." — Mark 11:33 (ASV)

And they answered and said to Jesus
Being reduced by this dilemma to the greatest strait and difficulty;

we cannot tell :
they could, if they would, but they did not want to tell; they knew if they did, they should expose themselves one way or other:

and Jesus answering, says to them, neither do I tell you by what
authority I do these things; (See Gill on Matthew 21:27).