[ Grammar ] How to use the word " effective " ? We regret to announce that Mr. Charles Appiah has resigned his position as senior sales manager,______ next Monday. (A) effect (B) effected (C) effectiveness (D) effective (E) efficient ——— M-W Learner's Dictionary http://www.learnersdictionary.com/definition/effective 3  : starting at a particular time — used to introduce a clause Effective [=starting, as of] tomorrow, the store will be open until 8:00 p.m. every day.
 Effective next month, the landfill will no longer accept old televisions.
 ——— Question: Q1: Can we explain the sentence as 『 We regret to announce that Mr. Charles Appiah has resigned his position as senior sales manager, ( which is / which will be ) effective next Monday. 』 and the antecedent of “ which ” is “ We regret to announce that Mr. Charles Appiah has resigned his position as senior sales manager ” ? or Is it just an idiomatic expression ? Q2: “ Effective tomorrow / next month,………. ” is a common expression in daily life ? Thanks