Children's toothbrushes may need to be changed more 13 .
答案：(B) frequently
【字彙】frequently 修飾 changed，表示兒童牙刷需要「更頻繁地」更換。essentially（本質上）、typically（典型地）、objectively（客觀地）均不符文意。
四個選項都是 -ly 結尾的副詞，形態一模一樣，你會覺得刷不掉，只好挑一個讀起來最順的。
四個選項都是副詞、都放得進 more 後面，形態這條路整個斷掉，可見這一格考的是語意。線索是同義勾環：前一句剛用 every three to four months（每三到四個月）講「多久換一支」，這一句 Children's toothbrushes may need to be changed more ______ 接著講同一件事，只是換一種說法，所以空格要的必定是一個講次數多寡的字。四個裡只有 frequently（頻繁地、經常）是頻率副詞。填進去讀成 changed more frequently（換得更勤），也就是比三到四個月更短的間隔。
typically（通常、一般而言）講的是「典型情況下」，帶一點「常常」的味道，形態又吻合，容易被順手選走，但它談的不是次數多寡；essentially（本質上、基本上）談的是事情的本質；objectively（客觀地）談的是看事情的態度，與整段無關。
frequently（頻繁地、經常）、every three to four months（每三到四個月）、replace A with B（用 B 換掉 A）、switch to（改用、換成）、typically（通常、一般而言）、essentially（本質上、基本上）。
Brushing your teeth regularly will help you maintain a healthy smile. But that smile won't last long if you don't take proper care of your toothbrush and switch to a new one often. According to the American Dental Association (ADA), toothbrushes can harbor bacteria. These germs come from the mouth and can 11 in toothbrushes over time.
Many Americans replace their toothbrushes only once or twice a year. The ADA, however, recommends 12 a new toothbrush every three to four months. Children's toothbrushes may need to be changed more 13 .
During those three to four months of use, there are several ways to keep a toothbrush clean. 14 , rinse your toothbrush thoroughly with tap water after use, making sure to remove any toothpaste and debris. Store your toothbrush in an upright position, and let 15 air dry. Most importantly, do not share toothbrushes.