Step 1: Understanding the Question:
We need the word closest in meaning to "iridescent".
Step 2: Key Formula or Approach:
Picture a real example of the word, such as a soap bubble or a butterfly wing, then match the quality that example shows against each option.
Step 3: Detailed Explanation:
A soap bubble looks iridescent because thin films of soap bend light and split it into shifting colors as you tilt it. That quality is a soft, glowing shine, not a fierce burst of light.
"Blaze" describes fire or a very strong burst of brightness, more intense than the gentle shimmer iridescence carries.
"Murkiness" is the opposite quality, describing dull, unclear surfaces such as muddy water.
"Illustration" refers to a picture or example, with no link to light at all.
"Luster" describes a soft glow or sheen, which is the closest match to the gentle, shifting shine of an iridescent surface.
Step 4: Final Answer:
The correct synonym for "iridescent" is "luster", so the answer is option (b).