What does x store?

a $=[2\mathrm{.}5,3\mathrm{.}5,[7\mathrm{.}5,8\mathrm{.}5,9\mathrm{.}5],[2\mathrm{.}2,3\mathrm{.}3,4\mathrm{.}4]]$

x $=$ a$[-1][1]$

Question $19$ options:

$9\mathrm{.}5$

x $=$ a$[-1][1]$ gives an IndexError

$[2\mathrm{.}2,3\mathrm{.}3,4\mathrm{.}4]$

$3\mathrm{.}3$