Alkenes express different reactivity with acids depending on concentration and temperature

The below images show when 1-butene reacts with different reagents (in d it's also H2SO4 not H2SO). My question is why are the two products different? 


I can get that in c), because it's more dilute there's more water to act as the nucleophile, and in d) there's more H2SO4 so that would act as the nucleophile but what's the role of temperature?


[![enter image description here](https://i.stack.imgur.com/bKfz6.png)](https://i.stack.imgur.com/bKfz6.png)


