Let $=\{$a$,$ b$,$ c$,$ d$\}$ be an alphabe,t and suppose that L consists of all strings of the form sup$($a$,)$; that is$,$ all strings consisting of as with at least $1$ a$.$ L$*,$ which means all strings can be formed by concatenating a finite number of strings from L$,$ including the empty string. Remember that L $+$ L means the set of all words that can be formed by concatenating two strings from L$.$ Which of the following is true?The shortest string in L$+$L has the length of $1$L$+$L does not contain the string $"$a$"$There are two different strings in L with the same lengthL$*=$ L