B. It shows where the previous sentence's information is from.
No they will not......
this is because after seeing caesar's ghost brutus may have some feeling of guilt.....guilt that caesar had loved him so much but he had betrayed him......that guilt will not let brutus fight willingly towards the opponents or maybe some other feeling in brutus's heart that to fully pay for this guilt he must die or he must kill himself......he might perform suicide ......after brutus's death caesar may also want to kill himself due to immense guilt of separating such friends and doing sinful deeds........
making the decision to march the army to Phillipi early after seeing caesar's ghost may have been too fast for such a big decision which would affect the probability of brutus and cassius winning the battle.....
HOPE IT HELPED !!