Correct Grammar w/ Demonstrative Adj.s

Question

I am reviewing content from my Spanish course and this question has me stumped:

Choose the sentence that is grammatically correct:

-Esa mesa es amarilla

-Aquellas mesa es amarilla

-Esta mesa es amarilla

-Esa mesa es amarilla

Answer 1

Firstly, the first and the last answer are the same. I was taught that "esa" in most cases means the same as "esta", so the first, third and fourth sentences are correct. Amarilla ends with "-a", because la mesa is feminine. The second sentence is incorect, because the word "aquellas" refers to more than one thing, so it should be just: Aquella mesa es amarilla.