It was midnight. A herculean task confronted the small army of liberty-loving men. Only four hours of darkness remained in which to work in secrecy toward fortifying the height. With the break of dawn, discovery was inevitable. For then all movements... on the crest of the hill would be plainly visible to the eyes of the British on board the men-of-war Falcon, Lively and Somerset, lying in Charles River, as well as to the enemy force occupying Copp's Hill, just across the stream.

(from "Bunker Hill" by Chelsea Curtis Fraser)

Which does the description "herculean" indicate about the army's task?

1. It will probably be discovered.

2. It will take longer than four hours.

3. It will be critical to the army's success.

4. It will be nearly impossible to complete.

4. It will be nearly impossible to complete.