In the word hammering, why is the final consonant not doubled before adding the suffix?
because the stress is on the first syllable of the base word hammer
because the suffix begins with a vowel
because the base word is x or w
because the base word does not end in consonant + vowel + consonant

In the word hammering the reason that the final consonant is not doubled before adding the suffix is because the suffix begins with a vowel. The rule says that you double the final consonant before y or before a suffix beginning with a vowel in a word of one syllable that ends in a single consonant preceded by a single vowel.

B) because the suffix begins with a vowel

I hope it helps, Regards.