I would go with A :
B forbids thr transpoartation union from striking sounds like ''hitting'' striking=hitting
C-if I m worng thne this wud the ans but I belive this all good but for the fact that it is quite redundant!
D the use of''striking and will forbid'' seem very awkward tense change and wrong meaning
E - same ... quite lacking in clarity...
A- the new contarct does some thing and what is that =it frobidz a strike by the T unon...
hope that helps!
the whole worldmakes way for the man who knows wer he's going... good luck