Combined drill
[建] 雙用鉆頭
?? 詞語組成解析
combined
[[k?m'baind]]
a. 結合的；組合的
drill
[dr?l]
n. 操練;鉆頭;軍事訓練;（應對緊急情況的）演習;
vt.& vi. 鉆（孔）;打（眼）;操練;訓練;
vt. 作…演習，操練;
??? 情景例句
Good night, Dad.
晚安， 爸爸。
In time of peace prepare for war.
居安思危。
and by measuring the time interval between the taps and the receipt of the echoes, the depth of the sea at that point can be calculated.
測出回聲間隔的時間，便可算出該處海洋的深度。