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

The production function $Y _ { t } = A _ { t } K _ { t } ^ { 1 / 3 } L _ { t } ^ { 2 / 3 }$ , where A_t is the stock of ideas, K_t is capital, and L_t is labor, assumes:

A) A_t is rivalrous
B) A_t is nonrivalrous
C) K_t is nonrivalrous
D) L_t is rivalrous
E) A_t is fixed