Question $2$

Express the number $0\mathrm{.}000191$ in scientific notation.

$1\mathrm{.}91{10}^{-6}$

$1\mathrm{.}91{10}^2$

$1\mathrm{.}91{10}^4$

$1\mathrm{.}91{10}^{-4}$

$1\mathrm{.}9110-3$