AV-shapedripplewiththepointoftheVpointingupstreaminarivermayindicatea（）.
A: submergedrock，notdangeroustonavigation
B: sunkenwreck，notdangeroustonavigation
C: towed-underbuoy
D: Alloftheabove
A: submergedrock，notdangeroustonavigation
B: sunkenwreck，notdangeroustonavigation
C: towed-underbuoy
D: Alloftheabove
举一反三
- He______invaintomakehiswifehappy. A: endeavored B: madeendeavor C: triedtheendeavor D: alloftheabove
- Waterskiing riders are towed behind a specially built speedboat.
- 下列四个关系式中哪一个不是麦克斯韦关系式？（） A: （aT/aV）=（aV/aS） B: （aT/ap）=（aV/aS） C: （aS/aV）=（ap/aT） D: （aS/ap）=-（aV/aT）
- Whentakingactiontoavoidcollision，youshould（）. A: Makesuretheactionistakeninenoughtime B: Notmakeanylargecoursechanges C: Notmakeanylargespeedchanges D: Alloftheabove
- Beforeenteringthechainlocker，youshould（）. A: havesomeonestandingby B: makesurethereissufficientairwithinthelocker C: de-energizethewindlass D: Alloftheabove