HELP PLS

“The boy sighed. His head fell back, his lower jaw dropping as if he had been surprised by something. A dull blankness slid slowly across his eyes. He was silent.”Which option best describes the meaning of the phrase “a dull blankless slid slowly across his eyes”?

A: The soldier began to cry.
B: The soldier went cross-eyed.
C: The soldier’s eyes started to water.
D: The soldier’s eyes glazed over as he died.