To avoid rejecting projects that actually should be accepted,

Intangible benefits should be ignored.

Conservative estimates of the intangible benefits' value should be incorporated into the NPV calculation.

Net present value should be calculated without regard to intangible benefits and then, if the NPV is negative, the present value of the intangible benefits should be estimated and compared to the amount of the negative NPV$.$

$1$

$2$

$3$

both $2$ and $3$ are correct