Which diagram shows lines that must be parallel lines cut by a transversal

see the attached figure with letter to better understand the problem

we know that

if the lines r and s are parallel

then

m∠c=m∠> by corresponding angles

therefore

the answer in the attached figure

answer: 4  

the square root of 16 is 4. it is a very simple mathematic concept. a square root when a number multiplied by itself will result in a number. here, the number 16 comes when 4 is multiplied by 4. hence the square root of 16 is 4. you can always figure out a square root by the inverse operation of squaring.