Extent of natural cross-pollination and the desired isolation distance are given. Find out the wrong one.

Isolation distance is the minimum separation required between two or more varieties of the same species for the purpose of keeping seed pure.
As a general rule, plants that primarily self-pollinate require less isolation distance, while plants that primarily cross-pollinate require greater distances.
Therefore None of the above options given is wrong as per the rule, that is the extent of natural cross-pollination is decreasing with decrease in distance.
When isolation distance is more that is 500 - 1000 meter, the extent of natural cross-pollination is maximum i.e. 50 - 75%.