What is the goal of a politician who uses “vague” language?

The use of vague language allows them to say things in a very generic way so that they can account for what they say, any more precise language can become compromising for them as they will be asked in the future to account for what they said, so a sentence like "we will do our best to erradicate corruption" is vague and if a politician is asked to account for this they can say "well, we have been doing our best but it is not easy", now if they say "we will erradicate corruption in our government within the next three years." people can ask them to account for these exact words.  

the answer is a).