How do you find the arc length of a semi-circle?

What is the slope of the line that contains the points (4,8) and (9,8)? what type of line is it?

5× 1/2 = ? a) more than 5 because you are multiplying by a whole number b) 5/10 because you multiply the numerator and denominator by 5 c) less than 5 because you are multiplying by a number that is more than 1 d) less than 5 because you are multiplying by a number that is less than 1

Can someone check if i did this correct. it’s number 4 if you’re wondering.