Though the passage and the statement you're being asked to evaluate seem relatively simple at first blush, they require a solid understanding of English and the definition of the words used to come up with the correct answer. We're being asked to evaluate this statement:
Wind power is popular with the UK general public. Yes? No? Not given?
Let's start with what our possible responses mean.
- Yes: There is at least one way that the passage could imply this statement is true.
- No: There is no way that the passage could imply this statement is true.
- Not Given: There is not enough information to determine the truth of this statement.
So to begin with, our answers are most permissive of an answer of Yes, and least with an answer of No, only yielding a Not Given in the case that no information correlates to the statement in question, so let's start with the UK general public? What in the full passage describes the general public?
This policy has found favor with the [general] public who support the search for cleaner energy sources.
Some have pointed out that without a comma after public that the meaning of the sentence is vague, and this is indeed true. In this configuration, it could be describing only a portion of the public. However, it could also describe the public as a whole. As this is a valid interpretation of the sentence, and we're asking merely whether there is any way the passage could imply the statement, we can say two things with confidence about the UK general public:
- They favor the issuing of wind farm licenses.
- They support the search for cleaner energy sources.
Now we need to tie these statements in to the concept of Wind Power. What does the passage have to say about wind power?
Wind power is seen [by the UK's government] to be the answer to [making good on its promise to generate 10% of its electricity using renewable sources].
This is directly tied to the issuing of wind farm licenses; and we've already established that the UK general public favors this. So let's see what kind of chain of logic that creates.
- The UK government has issued wind farm licenses.
- The UK general public favors this.
- Therefore, the UK general public favors wind farms.
- Furthermore, favor for wind farms implies favor for wind power in general.
- Additionally, the UK general public supports the search for cleaner energy sources.
- As wind power is a very clean energy source, it may be safely implied that the UK general public would support wind power as an energy source.
- Therefore, as the UK general public favors wind power, and supports wind power as an energy source, absent any arguments against either of these points, it is safe to assume that wind power is popular with the UK general public.
That final point is a bit more tenuous than those that precede it, so let's ask the relevant question: can something be supported or favored by a population without being popular?
The argument could be made that an entity (singular or plural) could support something that they dislike. For example, you may dislike dental visits; they can be expensive, annoying, and downright painful. Still, if you want healthy teeth, they are one of the best ways to accomplish this, so you begrudgingly support them.
For a population to favor something, on the other hand, a majority of that population must do so. As popularity is defined as something regarded with favor by people in general, we can equate the favor of a population with its popularity.
So, since there is a way that the passage could imply the statement to be true, the answer IELTS gives -- Yes -- is indeed justifiable. It's not the only interpretation, but it is a valid interpretation.