Hint:Think about the order of the letters when forming the consonant त्र
By writing र (ra) first and then adding the halant (्) to suppress its inherent vowel, then writing त (ta)
By writing त (ta) first, then adding the halant (्) to suppress its inherent vowel, then writing र (ra)
By writing त (ta) and र (ra) separately
By writing र (ra) and त (ta) together without a halant
Explanation
The correct order is to write त (ta) first, then add the halant (्) to suppress its inherent vowel, then write र (ra). The two then merge into the ligature त्र (tra).