Which activities are considered to be effective income splitting techniques?

$1.$ Gifting money to a lower$-$income spouse to invest.

$2.$ Lending money interest$-$free to your adult child to invest.

$3.$ Paying a salary to a family member working in one$$s business.

$4.$ Generating capital gains in the hands of one$$s child.

a$.$

$2$ and $4.$

b$.$

$1$ and $2.$

c$.$

$1$ and $3.$

d$.$

$3$ and $4.$