A． Because robots will not be able to communicate with life on Mars.
B． Because robots are not as good as human beings are at digging underground for life on Mars.
C． Because human beings are as intelligent as robots.
D． Because robots cannot set up colonies on Mars.

A． Because more people are living beyond their expectations.
B． Because scientist are very much interested in it.
C． Because more people are not living as long as they expected.
D． Because researchers found centenarians always have unconventional hobbies.