Question

select the allusion in the passage. the engineer had listened to the enthusiastic sailor developing these imaginative projects. to attack this mass of granite, even by mining, was a herculean task, and it was truly vexing that nature had not helped them in their necessity. but he answered pencroff, simply by proposing to examine the wall more attentively, from the mouth of the river to the angle which ended it to the north. from jules verne, journey to the centre of the earth submit

Explanation:

This phrase is an allusion to Hercules (Heracles), a figure from Greek mythology known for his immense strength and 12 nearly impossible labors. Referring to the mining task as "Herculean" draws on this mythic reference to emphasize the task's extreme difficulty.

Answer:

"was a Herculean task"