Goldenrod gall flies (Eurosta solidaginis) lay eggs on the stems of several plant species - Scottish Highers Biology - Question 8 - 2019

The correct answer is diagram B. This diagram illustrates stabilizing selection, where intermediate gall sizes are favored. In smaller galls, wasps predate more frequently, while larger galls are more vulnerable to bird predation. As a result, extreme gall sizes (either too small or too large) will decrease in frequency in the population, resulting in a more pronounced peak at intermediate gall sizes.