There are total 10 right angles in the given diagram, hence option (b) is correct match.
<em>Refer the attached image for clarification. </em>

I think every angle below 90 degrees
Alright!
The formula of area of a triangle is base x height /2
so you're given the height and hypotenuse.
Do the reverse of the pythagorean theorem to find the base
a^2= c^2 -b^2
c^2 is the hypotenuse and b^2 is the height
a^2= 10^2 - 8^2
a^2 = 100 - 84
a^2 = 16
a= (square root the 16)
a= 4 cm
now put these numbers into the formula for area of a triangle
bxh / 2
(4x8)/ 2
= 16 cm squared !!
hope that makes sense :)
There you go!!! Hope I helped :)