Consider the following statements with reference to structure of...

The thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents. Thus, statement 1 is correct.

The temperature at the tropopause over the equator is about $-80^{{}^{\circ}}\text{C}$, while over the poles it is about $-45^{{}^{\circ}}\text{C}$. Since $-45^{{}^{\circ}}\text{C}$ is greater than $-80^{{}^{\circ}}\text{C}$, the air temperature of the tropopause is highest above the poles. Thus, statement 2 is correct.

The temperature in the troposphere decreases at the rate of $1^{{}^{\circ}}\text{C}$ (not $1^{{}^{\circ}}\text{F}$) for every $165\text{ m}$ of height, which is known as the normal lapse rate. Thus, statement 3 is incorrect.

Therefore, only statements 1 and 2 are correct.

Answer: 1 and 2 only