What's the original reading in Mark 9:29?
"by prayer"
or
"by prayer and fasting"?
Both the external and the internal evidence overwhelmingly support the latter reading. It's probably time for our Critical Text friends to admit they were wrong to follow Aleph and B here and allow "and fasting" to return to the text rather than being relegated to the apparatus.
(This verse is a good test case to see if CT people are willing to abandon WH.)