Hi guys, I was told in the class, you can determine wether the CFG grammar is ambiguous by following the predict recursive decent parser's restriction.

for example G1: the First(aA) = {a}

First(a) = {a}

First(aA) intersect First(a) != empty set, therefore G1 should be ambiguous, but this is wrong, can I get some explanation

why using this restriction rule is not working on this problem, thanks

Q13. Which of the following grammars are ambiguous