未知题型 John is up to his eyes in work at the moment. The underlined word means______.A.very excitedB.very busyC.very tiredD.very efficient

未知题型 'Look at those pretty girls' skirts' is ______, because it is not clear whether the girls or the skirts are 'pretty'.A.ambiguousB.hiddenC.indirectD.indistinct

单项选择题 图示简支梁受到集中力作用（l = a+b），下列结论错误的是（  ）。