With the Production Function $Y _ { t } = A _ { t } K _ { t } ^ { 1 / 3 } L _ { t } ^ { 2 / 3 }$

With the production function $Y _ { t } = A _ { t } K _ { t } ^ { 1 / 3 } L _ { t } ^ { 2 / 3 }$ , if we double ________, we have an increasing returns production.

A) capital
B) capital and the stock of ideas
C) capital and labor
D) capital, labor, and the stock of ideas
E) labor and the stock of ideas