Write True or False.

Integers are not closed under subtraction.

Write True or False.

Additive identity of an integer $\mathrm{a}$ is $0$.

Write True or False.

Sum of two negative integers is a positive integer.

Write True or False.

$(\mathrm{a}-\mathrm{b})-\mathrm{c}=\mathrm{a}-(\mathrm{b}-\mathrm{c})$

Write True or False.

$\mathrm{a}+(-\mathrm{a})$ is always positive.

A bird watcher on a cliff spotted a kingfisher $7 \mathrm{m}$ above him. Earlier he had seen it $11 \mathrm{m}$ below him. What was the change in altitude of the kingfisher?