His plans may sound nebulous.

A. clear

B. concrete

C. prominent

D. conspicuous

Answer: Option A

Solution(By Examveda Team)

Nebulous : in the form of a cloud or haze; hazy.
Clear : easy to perceive, understand, or interpret.
Concrete : existing in a material or physical form; not abstract.
Prominent : important; famous.
Inconspicuous : not clearly visible or attracting attention.

Antonym of Nebulous is Clear