Fill in the blank to make the statement true:

$e$ {set of vowels} ( belongs to, not belongs to)

$7$ _____ {$x | x$ is a multiple of $7$} 

$m$ _____ $\{m, a, t\}$

The statement $1$  $\in x | x$ is a prime number, is _____ (true/false)

Fill in the blank with "belongs to or does not belong to" to make the statement true:

$0$ _____ {$5-5, 5+5, 5\times 5, 5÷5$}

$b$ _____ an element of {$c,o,p,y$}

State the cardinal number of the following set

$A=$set of letters in the word 'LOOK'.

State the cardinal number of the following set: 

$B=\left\{\mathrm{Triangle},\mathrm{quadrilateral},\mathrm{pentagon}\right\}$

State the cardinal number of the following set

$C=\left\{0\right\}$