Question

Which of the following is a compound sentence?

Robots that can perform simple tasks are becoming very popular.


Since the word “robot” refers to machines that can perform complex tasks, but is limited to machines whose tasks are not controlled by humans.


Because robots are machines that can perform complex tasks, a machine is not considered a robot if it performs only simple tasks.


Robots can perform different tasks, but they are limited by the number of tasks they can perform at one time.

Answer 1

The very last one. Compound means two independent clauses, or two sentences, put together. "Robots can prefrom different tasks," and "They are limited by the number of tasks they can preform at one time," can be sentences ALONE, but when put together (with a but, or, etc.) it becomes compound.