Choice "C" is correct. RST's net assets increased $115,000 as a result of the contribution of equity securities, the increase in market value and the dividends received is computed as follows:

All debt securities and those equity securities that have readily determinable fair values are measured at fair value in the statement of financial position. Gains and losses on investments are reported in the statement of activities. Investment income (e.g., dividends and interest) is reported in the period earned as an increase in net assets.
Choice "a" is incorrect. The proposed solution excludes changes in market value and dividends from increases in net assets in error. Both the change in market value and the dividend would be considered as an increase in net assets.
Choice "b" is incorrect. The proposed solution excludes changes in market value from increases in net assets in error. Both the change in market value and the dividend would be considered as an increase in net assets.
Choice "d" is incorrect. The proposed solution excludes dividends from increases in net assets in error. Both the change in market value and the dividend would be considered as an increase in net assets.