Answer
$b.$ and $d.$ are correct.
Work Step by Step
To write a percent as a decimal, we drop the % and move the decimal point two places to the left.
$a.$ is incorrect, because $6.5$%$=0.065$
$b.$ is correct, because $7.8$%$=0.078$
$c.$ is incorrect, because $120$%$=1.2$
$d.$ is correct, because $0.35$%$=0.0035$
