Using the words that are given in the bracket, combine the sentences given.
I went home. I found my dog missing. (on going)
(a) Going home, I found my dog missing.
(b) On going home, I found my dog missing.
(c) Going on home, I found my dog missing.
(d) I found my dog missing going home.

Hint: Our task here is to place the group of prepositions in a suitable position, while combining the given two statements. To complete this, first remember that neither one of the two words can be omitted, ‘on’ is the preposition and ‘going’ is the gerund. So we can clearly eliminate options that violate these rules. All we need to do now is find the right position to place the group of prepositions, remember that a gerund or a noun needs to come right after the preposition.

Complete answer:
All the options must be read multiple times, see which sounds best to you. To answer this question, we must remember that neither one of the two words can be omitted, nor can the order of the words in the preposition change. Also when two separate sentences are asked to be put together, take note that always a noun or a gerund comes after the preposition.
Look at option (a) it’s incorrect; as the preposition ‘on’ has completely been removed from the sentence, so at one look this option can be omitted.
Look at option (b) it’s correct; the placement is perfect since the preposition ‘on’ as per requirement, is followed by ‘going’ the gerund and so it is grammatically correct. This has replaced ‘I went’ in the first sentence.
Look at option (c) it’s incorrect; the meaning of the sentence has been changed, this sentence means that he forgot to take his dog back home, but the question says that he left the dog at home itself, but the dog has left his house.
Look at option (d) it’s incorrect; no part of this sentence is grammatically acceptable.
So the correct way of using the preposition is in option (b).

Thus the correct answer is option ‘b’ i.e, On going home, I found my dog missing.

Note: Keep in mind that prepositions are those words in a sentence that can connect nouns, pronouns, or various other words. They are used to describe a situation, moments when something happens, or to give instructions. They may not necessarily have the same meaning or the same use in different sentences.