$1)$What is the $r$ code for checking missing values in a dataset?

A$)$is$.$na$($Bat Bat$==""$

$($B$)$ colnames$($Bat$)[$apply$($is$.$na$($Bat$),2,$ any$)]$

$($C$)$ Bat$[$is$.$na$($Bat$)]=$Mode$($Bat$)$

$($D$)$ Bat$[$is$.$na$($Bat$)]=$mean$($Bat$,$na$.$rm$=$TRUE$)$

$2)$A statistician stored data in $R$ and named it BreastCancer$\_$dat. The columns of the data are age, weight, blood, glulevel, and education. What is the $r$ code for selecting the weight column?

$($A$)$ Breast.Cancer$\_$data$weight

$($B$)$ breastCancer$\_$data$weight

$($C$)$ BreastCancer$\_$dat$weight

$($D$)$ Breast.cancer$data$weight

$3)$There is a matrix named Flower in $R$ with $3$ rows and $4$ columns. What is the $r$ code for selecting only thethird column?

$($A$)$ Flower $[,2]$

$($B$)$ flower$[3,]$

$($C$)A[,3]$

$($D$)$ Flower$[,3]$