The correct answer is D) 48.0 (psia). The vapor pressure of ethylene oxide at 46°C is 48.0 psia (pounds per square inch absolute). This can be determined from standard vapor pressure tables or calculations for ethylene oxide, which is a common industrial chemical. The high vapor pressure of 48.0 psia at 46°C indicates that ethylene oxide is a highly volatile substance that requires special handling and storage precautions. The other answer choices are incorrect because they do not accurately reflect the known vapor pressure of ethylene oxide at the given temperature of 46°C. Knowing the proper vapor pressure is crucial for safely handling and transporting hazardous materials like ethylene oxide on vessels, which is an important topic covered in the US Coast Guard Captain's License Examinations.