In this task, you need to answer the given multiple-choice question on the physics. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

[EX Q]: Problem: a hollow iron pipe is 21 cm long and its external diameter is 8 cm . if the thickness of the pipe is 1 cm and iron weights 8 g / cm cube , then find the weight of the pipe . 
Options: ['a ) 3.696 kg', 'b ) 3.686 kg', 'c ) 2.696 kg', 'd ) 2.686 kg', 'e ) none of these']
[EX A]: a

[EX Q]: Problem: hcf and lcm two numbers are 20 and 396 respectively . if one of the numbers is 36 , then the other number is ? 
Options: a ) 36 , b ) 66 , c ) 132 , d ) 264 , e ) 220
[EX A]: e

[EX Q]: Problem: which greatest possible length can be used to measure exactly 10 meter 40 cm , 14 meter 10 cm and 7 meter 90 cm 
Options: a ) 45 cm , b ) 25 cm , c ) 24 cm , d ) 15 cm , e ) 10 cm
[EX A]:
e