Which choice is equivalent to the expression below? Square root -20

What is the missing step in this proof ?

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

Factor the polynomial. b^2 + 4b + 4