Question

what is a common feature of careers in mining and drilling? long periods of concentration on the same task short and varied tasks limited use of heavy machinery

Explanation:

Mining and drilling involve repetitive operations like extracting resources or creating boreholes. These tasks demand sustained focus on one activity over time. Short - varied tasks don't fit as operations are more routine. Heavy machinery is extensively used, so "limited use" is incorrect.

Answer:

long periods of concentration on the same task