Question

Sara

英語の質問です。
文中(2)が　　were になる理由の解説を詳しくお願いします。

that time. The Alps (2) (was, were) a (3) challenging environment, with
steep slopes and very high places. However, after years of planning, almost
20,000 people worked by hand for six years to achieve (4) the impossible. (5)

英語 高校 文法