There are many alternatives to fossil fuels. For instance wind and solar.

This may appear to be two sentences, but the second ‘sentence’ does not contain a verb and is technically not a sentence. It’s the kind of thing you’ll occasionally hear in spoken English, but not in formal writing.

These are your options for IELTS Writing Task 2:

• There are many alternatives to fossil fuels, for instance wind and solar.
• A is true. For instance, + sentence.
• There are many alternatives to fossil fuels. For instance wind and solar are becoming more and more efficient and cost effective.
• A is true, for instance + noun.

The structure used in the opening example (above) is NOT recommended:

• A is true. For instance, + noun.