You should not insert a conjunction after the second sentence because the instruction states that there are two sentences combined. Therefore, the end of the second sentence is the end of the idea. There are no elements for the conjunction to relate. If it was added, the cojunction would be left there hanging and the sentence would be grammatically incorrect (see 1 and 2).
1) Yesterday it rained all day long; therefore, I stayed at home
2) Yesterday it rained all day long, I stayed at home therefore*
Though he is filled with grief upon hearing his wife’s
death, Brutus remains focused on the war and instead concentrates on the war.
All while maintaining his composure even those his heart is full of sorrow. In
the end, he dies by committing suicide.
