A team from a foreign university studied 102 different kinds of venomous snakes, investigated their venom, food and habitat, and found that snakes living in a three-dimensional environment such as trees or water are less toxic than snakes in a two-dimensional environment (that is, ground). The researchers speculate that this is because snakes living in a three-dimensional environment encounter more things, encounter prey more frequently, and do not need highly toxic venom to ensure that each hunt is successful.
The statement 'The prey encountered in the trees or in the water is much smaller than that on the ground, and snakes need to hunt more to feed' is the most likely to question the researchers' conjecture.