Choose the best answer for the blank numbered (1) in the reading passage

Worker robots are becoming more (1) ___ in industries. Nowadays they can do more difficult jobs in many factories. The use of robots helps factories (2) ___ the quality of their products because robots can do the job well for many hours (3) ___ humans can get tired and bored.

Engineers can make robots more (4) ___ and useful at home, at school and at work. However, a robot uses (5) ___ about 100 times more energy than a human to do the same job. The latest 20 kg robot can lift 2 kg, but a 5kg human arm can lift 50 kg.