If the probability of defective bolts is 0.05 the standard deviation for the distribution of defective bolts in total of 1000 bolts is :

$5\sqrt{1.9}$

The correct answer is Option (3) → $5\sqrt{1.9}$

for a binomial distribution, the standard deviation ($σ$) is,

$σ=\sqrt{np(1-p)}$

$=\sqrt{1000×0.05×(1-0.05)}$

$≃6.89≃5\sqrt{1.9}$