Answer:
There will be an evolution of larger, deeper beaks.
Step-by-step explanation:
Since Tribulus cistoides is the most abundant food in their new environment, the medium ground finches with larger, deeper beaks within the population will be favoured by natural selection.
This group of medium ground finches will multiply and contribute more to successive generations as compared to their weaker counterparts with less large and deep beaks. The later group gradually fades off the population as a result of been less adapted to cracking and eating the tough Tribulus cistoides fruits.
Hence, with time, evolution of larger and deeper beaks will take place in the population.