Answer:
length of diagonal d is 50 m. (first option is correct)
Explanation:
using pythagoras theorem
here 40 and 30 are the legs of the triangle so let them be a and b respctively.
And d is the hypotenuse so let it be c
a^2 + b^2 = c^2
40^2 + 30 ^2 = d^2
1600 + 900 = d^2
2500 = d^2
50 = d