How many letters does the top answer for “easy to believe on the basis of available evidence” have?

The most common answer is credibly (8 letters).

Crossword clue: easy to believe on the basis of available evidence

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

credibly 8 letters wn-def

easy to believe on the basis of available evidence

plausibly 9 letters wn-def

easy to believe on the basis of available evidence