Which of the following are examples of real options? $1.1)$ the option to expand if an investment project succeeds

$2.2)$ the option to wait $($and learn$)$ before investing

$3.3)$ the option to shrink or abandon a project

$4.4)$ the option to vary the mix of output or the firm's production methods

A$)1,2,3,$ and $4$

B$)1$ and $2$ only