Isohels are the isopleths of sunshine. Isopleths are lines of equal value on a map, indicating a specific attribute or variable. In the case of isohels, they represent lines of equal sunshine duration. So, if you were to draw isohels on a map, all points along a particular isohel line would receive the same amount of sunshine. This can be used to visually represent variations in sunshine duration across a region. It is important to note that the other options presented in the question are not correct representations of isohels. Flowering time, rain, and clouds are not related to isohels. Therefore, the correct answer is option 1.