Then it flies $1200 \,m$ upward so $r = \sqrt {{{(100)}^2} + {{(1200)}^2}} $
$ = 1204\,m \simeq 1200\,m$
The option should be $1204\, m$, because this value mislead one into thinking that net displacement is in upward direction only.
(બંને ટ્રેક વચ્ચેનું અંતર નહિવત લો)