Despite the best efforts of astronomers, no one has yet succeeded in exchanging messages with intelligent life on other planets or in other solar systems. In fact, no one has even managed to prove that any kind of extraterrestrial life exists. Thus, there is clearly no intelligent life anywhere but on Earth.
The argument’s reasoning is flawed because the argument
(A) fails to consider that there might be extraterrestrial forms of intelligence that are not living beings - WRONG. Irrelevant. Argument is about life only.
(B) confuses an absence of evidence for a hypothesis with the existence of evidence against the hypothesis - CORRECT. Argument concludes based on absence of evidence and hypothesize that there is no intelligent life anywhere but Earth.
(C) interprets a disagreement over a scientific theory as a disproof of that theory - WRONG. It takes into account that astronomers were not able to find extraterrestrial life and thus bases its conclusion on that fact.
(D) makes an inference that relies on the vagueness of the term “life” - WRONG. Argument does not define life.
(E) relies on a weak analogy rather than on evidence to draw a conclusion - WRONG. Argument does not draw any analogy.
IMO Answer B.