Step 1: Understanding the relationship between "GRAIN" and "SALT".
A grain of salt is a small unit of salt, just as a chip of glass is a small unit of glass. This implies a relationship where the first word is a small unit or piece of the second word.
Step 2: Analyzing the options.
(A) shard : pottery: A shard is a broken piece of pottery, but the relationship is not the same as that of a grain of salt.
(B) shred : wood: A shred is a small piece of wood, but the relationship does not quite match the idea of a "grain" being a unit of something.
(C) blades : grass: A blade of grass is a single piece of grass, but it doesn't match the "grain" and "salt" relationship exactly.
(D) chip : glass: Correct — A chip of glass is a small piece of glass, which is similar to a grain of salt being a small piece of salt.
Step 3: Conclusion.
The correct answer is (D) chip : glass, as it has the same relationship as "GRAIN : SALT".