Which geographical feature borders southern texas on the eastern side?

The geographical feature which borders the Southern Texas on the eastern side is the Gulf of Mexico. The Gulf of Mexico is an ocean basin and a marginal sea of the Atlantic Ocean. It is largely surrounded by the North American continent. In the northeast, north and northwest, the Gulf of the United States is located. Mexico on the other hand, is in the southwest and south portion while Cuba is in the southeast.  The Gulf of the North is bordered by Alabama, Florida, Louisiana, Mississippi and Texas border the Gulf on the north. These are often referred to as the Third Coast. The Gulf of Mexico is one of the gulf’s main areas. 

i believe your answer is d)