Write an Equivalent Double Integral with the Order of Integration $\int _ { 0 } ^ { 9 } \int _ { 0 } ^ { x } d y d x$

Multiple Choice

Write an equivalent double integral with the order of integration reversed.
- $\int _ { 0 } ^ { 9 } \int _ { 0 } ^ { x } d y d x$

A) $\int _ { 0 } ^ { 9 } \int _ { - 9 } ^ { y } d x d y$
B) $\int _ { 0 } ^ { 9 } \int _ { y } ^ { 9 } d x d y$
C) $\int _ { 0 } ^ { x } \int _ { 0 } ^ { 9 } d x d y$
D) $\int _ { 0 } ^ { 9 } \int _ { 9 } ^ { y } d x d y$