Is it correct to say on/at the weekends instead of saying on/at weekends?

Read the excerpt from the war of the worlds.a large portion of the cylinder had been uncovered, though its lower end was still embedded. as soon as ogilvy saw me among the staring crowd on the edge of the pit he called to me to come down, and asked me if i would mind going over to see lord hilton, the lord of the manor. the growing crowd, he said, was becoming a serious impediment to their excavations, especially the boys.which context clues effectively indicate the meaning of the word excavations as it is used in the excerpt? (select all that apply.)edge of the pitamong the staring crowdhad been uncoveredwas still embedded