The correct spelling of prefer+ -ing is <em>preferring</em>.
In general, we double the last consonant of the root word when adding a suffix starting in a vowel if:
- the root word ends with a vowel followed by a single consonant:
prefer + -ed → preferred
cancel + -ed →cancelled
target + -ing→ targetting
win + -ing→ winning
beg + -ing→ begging
wet + -ing→ wetting
- The word is accented on the last syllable:
Forget + -ing → forgetting
Submit + -ing→ submitting
In the case of <em>preferring</em>, when adding the suffix -ing to <em>prefer</em>, we double the consonant r because it is a two-syllable word ending with a single vowel that is followed by a consonant.
You can learn more about suffix -ing in the link below:
brainly.com/question/1250119
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