The only purpose of ______ activity is the instantaneous increase of sales.?

(C) sales-promotion=compound noun--->for sales promotion activity---> for the instantaneous increase of sales made more clear.

activity是名詞所以需形容詞修飾或複合名詞（名詞+名詞），經分析修正如下：
promotion>promotional,publicity>public
sales promotion>sales-promotion，沒有三個名詞形成複合名詞
advertising 分詞當形容詞正確✅
salespeople>salespeople’s

The only purpose of advertising activity is the instantaneous increase of sales. Yip

正確答案是 (C): sales promotion
問題既然明確指出 "the instantaneous increase of sales"，sales promotion activity 是唯一為了刺激銷售為目的的促銷活動，例如 Free Samples、Loyalty Programs、Premiums、Sweepstakes、Product Demonstrations...

為什麼不是 (A) promotion
advertising、personal selling or telemarketing、publicity 、direct marketing，都屬於 "promotional activity"，也就是說，答案B、C、D、E 都是promotion的內容項目。

C. sales promotion / 對應立即的增加sales，用該詞比(A)來的清楚明確,B.D.E無確定直接關連