To answer your question about the difference between B and C...
There has been some speculation that the severed engine of the airplane might have struck the tail, but investigators will withhold judgment until they examined further the engine's strike marks and its cause.
B will withhold judgment until they have further examined the strike marks on the engine and their cause. Correct one. The examiners will examine the strike marks. and the cause of these
(i am using plural form here, to show that ITS cannot be used) marks. This is though collective, the examiners have to examine individual marks.
C will withhold judgment until they have further examined the cause for the strike marks and the engine - This one sounds like they will do 2 examinations, one is the cause for the strike marks, and another examination of the engine. But the orginal sentence is intend to say that there is only one examination, which is the STRIKE MARKS (the cause etc..the subject is just one, the STRIKE MARKS)
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D have withheld the judgment while there was a further examination of the strike marks on the engine and its cause - sounds like the examiners have withheld, while the examination is going on, changes the meaning. Hence wrong.
E have withheld judgment until further examination of the engine, the strike marks, and the cause- tense problem. Hence wrong.
I hope that helps.
Giving another SHOT