# The average (arithmetic mean) of $3^{30}, 3^{60} \text { and } 3^{90}$ is.

A. $3^{27}+3^{57}+3^{87}$

B. $3^{29}+3^{59}+3^{89}$

C. $3^{60}$

D. $3^{177}$

$\begin{array}{l}\text{ According to the question, }\\ \Rightarrow\Large\frac{3^{30}+3^{60}+3^{90}}{3}\\ \Rightarrow3^{29}+3^{59}+3^{89}\end{array}$