Question

Assuming that the sentence follows the phrase structure rules given below, decide whether the sentence is a kernel sentence or a transform. S NP + VP. NP (DET) N VP V (NP) Did Mr. Brown teach his class?

Answer 1

The sentence doesn't follow the phrase structure rules given above, which means that it is a transform sentence, not a kernel one.
A kernel sentence always has to be active and declarative. The second part means that it cannot be a question, but rather a statement. Here, as you can see, the example is a question, which means that it cannot be a kernel sentence.