取自某本proofreading 的書:(以下是對左答案的內容)
Everyone prefers numbers that seem to be easy to remember, and many people like their phone number and pager number to be the same as their birth dates. Some customers have personal lucky numbers and insist that the digits in their phone numbers add up to these.
句子中出現的四個 number,
第一個number 要加 s, 我大致上都feel 到點解。因為每個人prefers 的number, 即係好多number, 所以加 s.
第二、三、四個, 佢地前面都有 their , 但為何只有第四個number 才要加s呢?