Strings are special sequences that are used a lot in CS $420.$ Which of the following are sequences?

$($select all that apply$)$

The following checkbox options contain math elements, so you may need to read them in your screen reader's $$reading$$ or $$browse$$ mode instead of $$forms$$ or $$focus$$ mode.

Choice $1$ of $4$:the empty string

$$

$\backslash$epsi

Choice $2$ of $4$:the string

abcdefg

abcdefg

Choice $3$ of $4$:any string

Choice $4$ of $4$:all possible strings $($over some alphabet$)$ written in lexicographic order