Step 1: Understand the question.
In Sanskrit phonetics, each sound is named by the place in the mouth where it is made. We must put four letters in the order Kanthya (throat), Oshthya (lips), Murdhanya (roof of the mouth) and Dantya (teeth).
Step 2: Find the place of each letter.
'ka' is a velar sound made at the throat, so it is Kanthya (D). 'pa' is made with the two lips, so it is Oshthya (A). 'ra' is made with the tongue at the hard palate or roof, so it is Murdhanya (C). 'ta' is made with the tongue at the teeth, so it is Dantya (B).
Step 3: Build the sequence.
Kanthya is D, Oshthya is A, Murdhanya is C and Dantya is B. The sequence is D, A, C, B.
Step 4: Check option 1, A, B, C, D.
This starts with the lip sound pa instead of the throat sound ka. So it is wrong.
Step 5: Check option 2, A, B, D, C.
This also starts with pa and puts the throat sound third. So it is wrong.
Step 6: Check option 3, B, A, D, C.
This starts with the teeth sound ta. The required first letter is the throat sound ka, so it is wrong.
Step 7: Check option 4, D, A, C, B.
This gives ka, pa, ra, ta, which is throat, lips, roof of mouth and teeth. It matches the question, so option 4 is correct.
Final Answer:
The order is ka, pa, ra, ta, which is D, A, C, B. This is option 4.
\[ \boxed{\text{D, A, C, B (option 4)}} \]