Consider the following class:

class Desk $\{$ private Drawer$[]$ drawers; public void openDrawer$($int drawerNumber$)\{//...\}$ public void closeDrawer$($int drawerNumber$)\{//...\}$ public boolean isOpen$($int drawerNumber$)\{//...\}$ public void add $($Junk j$,$ int toDrawer$)\{//...\}$ public Junk removeRandomItem$($int fromDrawer$)\{//...\}\}$

Which functions of this class are missing a non$-$trivial pre$-$condition?

Group of answer choices

$$closeDrawer

removeRandomItem

isOpen

add

$$openDrawer