[The following information applies to the questions displayed below.) On October 12, 2017, Neptune Corporation invested $700,000 in short-term available-for-sale marketable securities. The market value of this investment was $730,000 at December 31, 2017, but had slipped to $725,000 by December 31, 2018. Assuming Neptune does not sell this investment, the fair value accounting adjustment necessary at December 31, 2018, includes: Select one: O a. A $5,000 debit to Unrealized Holding Gain on Investments. b. A $25,000 credit to Unrealized Holding Gain on Investments. Oc. A $5,000 debit to Investments in Marketable Securities. Od. A $725,000 debit to Investments in Marketable Securities.