If the Earth was formed billions of years ago, then why is this year still called as 2020?

The full name for our year is 2020 A.D., which stands for Anno Domini or "in the year of our Lord". This began at the birth of Christ. So, when we say we're in the year 2020, what we're really saying is that it's been 2020 years since the birth of Christ.

conditioned stimulus (CS).

Explanation:

Classical conditioning is a learning process, it was discovered by Iván Pavlov and today it is still under study.

The learning through Classical conditioning is carried out in the following way: we can generate learning when we establish an association between a conditioned stimulus and a neutral stimulus to obtain an unconditional response.

In this case, the real estate agent made an association through classic conditioning between the house and the delicious food, so when the client thinks about the house he will remember the delicious food and feel joy.

I hope this information can help you.