Deep-sea jellyfish are faintly luminous, and biologists still debate what advantage the glow provides at such depths.
深海水母会发出微光，生物学家仍在争论这种发光在如此深度有何益处。
Which choice best defines “luminous”?
C — Emitting or reflecting light; bright.. “luminous” means Emitting or reflecting light; bright..
Which word means “Emitting or reflecting light; bright.”?
D — luminous. “luminous” means Emitting or reflecting light; bright..
luminous — Emitting or reflecting light; bright.. In Chinese: 发光的；明亮的.
luminous is pronounced //ˈluːmɪnəs//.
Deep-sea jellyfish are faintly luminous, and biologists still debate what advantage the glow provides at such depths. (深海水母会发出微光，生物学家仍在争论这种发光在如此深度有何益处。)
glowing, radiant, brilliant — all close in meaning to luminous (Emitting or reflecting light; bright.).
dim, opaque — each the opposite of luminous (Emitting or reflecting light; bright.).
Yes. luminous is on the SAT Prep Difficult list — the higher-register words that decide the hard questions. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.
lumin(光) → 亮堂堂。