• Although --- used to express contrast or concession.
• Unless --- means “except if” or “if not”.
• As --- means “in the same way that” or “because”, depending on context.
• Since --- means “from a particular time in the past until now” or “because”.
We shall examine each sentence individually.
Step 1: Analyze sentence (A).
The sentence is:
\[
\text{He has changed a lot _ _ _ _ I last saw him.}
\]
The present perfect tense “has changed” indicates a change that has occurred from a point in the past until the present.
The word that correctly expresses this idea is:
\[
{\text{since}}
\]
Thus,
\[
(A) \rightarrow (IV)
\]
and the completed sentence becomes:
\[
\text{He has changed a lot since I last saw him.}
\]
This sentence is grammatically correct and meaningful.
Step 2: Analyze sentence (B).
The sentence is:
\[
\text{She arrived on time _ _ _ _ it was raining cats and dogs.}
\]
The phrase “raining cats and dogs” means raining very heavily.
The sentence conveys a contrast:
\[
\text{She arrived on time despite the heavy rain.}
\]
The conjunction that expresses contrast is:
\[
{\text{although}}
\]
Therefore,
\[
(B) \rightarrow (I)
\]
and the complete sentence becomes:
\[
\text{She arrived on time although it was raining cats and dogs.}
\]
Step 3: Analyze sentence (C).
The sentence is:
\[
\text{ _ _ _ _ there is an emergency, don't disturb me.}
\]
The intended meaning is:
\[
\text{Do not disturb me except in an emergency.}
\]
The conjunction that gives this meaning is:
\[
{\text{unless}}
\]
Thus,
\[
(C) \rightarrow (II)
\]
and the sentence becomes:
\[
\text{Unless there is an emergency, don't disturb me.}
\]
This is grammatically correct and logically meaningful.
Step 4: Analyze sentence (D).
The sentence is:
\[
\text{Do unto others _ _ _ _ you would have them do unto you.}
\]
This is a famous proverb.
The correct expression is:
\[
\text{Do unto others as you would have them do unto you.}
\]
Hence,
\[
(D) \rightarrow (III)
\]
where the appropriate word is:
\[
{\text{as}}
\]
Step 5: Compile the final matching.
From the above analysis, we obtain:
\[
(A)\rightarrow(IV)
\]
\[
(B)\rightarrow(I)
\]
\[
(C)\rightarrow(II)
\]
\[
(D)\rightarrow(III)
\]
Therefore the correct arrangement is:
\[
{(A)-(IV),\ (B)-(I),\ (C)-(II),\ (D)-(III)}
\]
which corresponds to
\[
{\text{Option (C)}}
\]