Consider the grammar g1: s → ε, s → as, s → asbs and the language l that contains exactly those strings of a's and b's such that every prefix has at least as many a's as b's. we want to prove the claim: g1 generates all strings in l. we take the following inductive hypothesis to prove the claim: for n < k, g1 generates every string of length n in l. to prove the inductive step we argue as follows: "for each string w in l either ) or ) holds. in both cases we use the inductive hypothesis and one of the rules to show that string w can be generated by the grammar. in the first case we use rule s → as and in the second case we use rule s → asbs." which phrases can replace the so that this argument is correct