Answer:
Option A, The cost-per-click on ad extensions is lower than on a search ad headline
Explanation:
Ad extensions provide better user interactions options and they allow people to take direct action from the search results.
More clicks can easily be obtained through ad extension and make an add cost effective (by reducing the cost incurred per click) and appealing. With reduced cost per click, as extension also guarantee higher engagement for advertisers and hence increase influence and quality
Hence, option A is correct
