The factor that would have the net effect of making a place warmer during summer would be that it is in the middle of a landmass.
The reason why a warmer summer would be present at the middle of a landmass is because landmass:
1. Has a lower specific heat capacity, and therefore can be heated up quickly, through receiving insolation from the sun.
2. Land is opaque, therefore insolation only concentrate in shallow areas, making the surface temperature increase.
3. There is no mixing of warm and cold layers, along with the lack of presence of evaporation, there would be less cooling
In sum, the above effects can be called continental climate, and thus the middle of a land mass is cooler.
For your reference, here's why the other options are not correct:
At a high elevation near an ocean - near the ocean would mean it has a maritime effect and therefore a cooler summer.
At a high latitude - with the less dense air, heat will be absorbed faster resulting in faster heat loss hence a cooler summer.
Hope it helps!
