Quirion ranger

[Mulletus]

if i activate the ranger my opponent cant wasteland the land i targeted can he?

[Jaiminho]

First of all, there is only one target to that ability and that's a creature. If it doesn't explicitly says the word "target", then it's not a target.

Then, you have the "return a land". Since it's part of the cost, no one can ever respond to it as you do those as a requirement to put the ability on the stack. In other words, you need to have a land in play to activate the ability and after it's considered played (the ability has been put on the stack and people can now respond), the land has already been returned to your hand.

Now, reponding to the actual question, he can't activate Wasteland targetting the land you returned since when he would get priority after you played the ability, the land has already been returned to your hand.