If 1K × K1 = K2K, the letter K stands for the digit.

We have,

Let us check for option (A), if K = 1,

We can see that the answer matches in the end.

So, we can conclude that K = 1 is the suitable answer.

Now, check for other options,

For (B), when K = 2,

We can see that it clearly doesn’t matches the final answer.

Option (B) doesn’t fit the answer.

For (C), when K = 3,

Clearly, the answer doesn’t match.

Option (C) is not the answer,

For (D), when K = 4,

Clearly, the answer doesn’t match.

Option (C) is not the answer,