As part of the ancient roman army, the cornicen sounded signals on an instrument called the

The correct answer is - cornu.

The cornicen was using an instrument cornu, after which he got the name. The cornicen was a junior officer at the Roman Imperial Army, and his role was to signal the salutes for the officers of the army, and more importantly to use the signals from the cornu as orders for the legions who of course new what each sound meant. The corniciens were always at the head of the centuries, along side the signifier and the tesserary.

the correct answer is b, "fertility rates are increasing, so populations will grow more quickly in the future."