Define a sequence and give $an$ example.

Choose the correct answer below.

$A.$ A sequence $\{a_n\}isan$ ordered list $of$ numbers $of$ the form $\{a_1,a_2,a_3,$dots,$a_n,$dots$\}.$ For example, $\{1,3,5,$dots$\}is$ a sequence.

$B.$

A sequence $\{a_n\}isan$ infinite sum $of$ the form $a_1+a_2+a_3+$cdots$={\displaystyle \underset{k=1}{\overset{}{}}}{a}_k.$ For example, $2+3+4+$cdots$={\displaystyle \underset{k=1}{\overset{}{}}}(k+1)is$ a sequence.

$C.$ A sequence $\{a_n\}isan$ increasing finite set $of$ numbers $\{a_1,a_2,a_3,$dots,$a_n\}$ such that $400\{a_n\}\{a_1,a_2,a_3,$dots,$a_n\}\{5,19,400,2,17\}{a}_1.$ For example, $\{2,5,17,19,$

$400\}is$ a sequence.

$D.$ A sequence $\{a_n\}is$ a finite set $of$ numbers $\{a_1,a_2,a_3,$dots,$a_n\}.$ For example, $\{5,19,400,2,17\}is$ a sequence.