Question 6 at the MSE-biology 9 (methods)

The first suggested answer is the method of description.

The second - so it will be: the method of comparison. At worst, microscopy.

The fourth answer is the measurement method.

Conclusion: the correct answer is No. 3.

The experiment requires intervention. In the formation of a conditioned reflex bell (conditioned stimulus) is turned on together with the appearance of the unconditioned stimulus (food for example).