It plans to stop delivering mail on Saturdays, 16 Aug. 1 this year.
答案：(C) starting
【分詞構句】逗號後以現在分詞 starting Aug. 1 補充說明「自8月1日起」，屬分詞片語修飾整句。starts 為限定動詞，不能接在逗號後單獨補充說明；started 時態不合（政策尚未生效）；to start 不定詞不符合此處表達「生效起始時間」的慣用句法。
四個選項是同一個字 start 的四種形態排在一起，你會直覺認定這是文法題，開始找主詞、判主動被動。
先看句子結構：逗號前的 It plans to stop delivering mail on Saturdays 已經是完整的句子，主詞 It 與動詞 plans 都在，逗號後不可能再放一個限定動詞，所以 starts 與 started 先出局。剩下 starting 與 to start，再看它們後面接的是什麼——Aug. 1 this year（今年八月一日）是一個時間點。starting 後面直接接一個時間點時，作用是標出起算的那一天，意思是「自……起」；換成 beginning Aug. 1 或 as of Aug. 1，意思完全一樣。填進去讀成 stop delivering mail on Saturdays, starting Aug. 1 this year（自今年八月一日起，週六不再送信）。鑑別度只有 31，但它本身不難：光是「逗號後不能再放一個限定動詞」這一關就刷掉一半選項，各種程度的人都答得出來，題目自然分不出高低。
starts 與 started 都是限定動詞，前面沒有連接詞就不能接在一個完整句子後面；to start 表目的（為了開始），但停送信並不是「為了開始八月一日」，語意接不上。
starting ＋ 時間（自……起）、beginning ＋ 時間（自……起）、as of ＋ 時間（自……起）、stop ＋ V-ing（停止做某事，對照 stop to V 停下來去做某事）、plan to V（打算做某事）、deliver mail（送信、投遞郵件）。
The U.S. Postal Service has been struggling financially for some time. It plans to stop delivering mail on Saturdays, 16 Aug. 1 this year. This decision was announced on Wednesday without congressional approval. 17 forbidden to do so by the Congress, the agency for the first time will deliver mail only Monday through Friday. It is expected that this 18 will save about $2 billion a year.
In recent years, the postal service has suffered tens of billions of dollars in losses 19 the increasing popularity of the Internet and e-commerce.
The postal service plans to continue Saturday delivery of packages, which remain a profitable and growing part of the delivery business. Post offices would remain open on Saturdays 20 customers can drop off mail or packages, buy postage stamps, or access their post office boxes. But hours would likely be reduced at thousands of smaller locations.