Suppose the quarterly arithmetic average return for a security is $5\%$ per quarter and the security gives a return of $10\%$ each over the next two quarters. The arithmetic average return over the six quarters isA$\mathrm{.}9\%.$ B$\mathrm{.}7\mathrm{.}5\%.$ C$\mathrm{.}6\mathrm{.}67\%.$ D$.10\%.$