Concept:
A compound proposition is a proposition formed by combining two or more simple propositions with logical connectives such as:
\[
\text{and, or, if...then, unless, neither...nor}
\]
A simple proposition contains only one basic assertion.
Step 1: Check statement A.
Statement A is:
\[
\text{Unless it rains in time, harvest will not be good.}
\]
The word unless expresses a conditional relation.
It can be understood as:
\[
\text{If it does not rain in time, then harvest will not be good.}
\]
So, A is a compound proposition.
\[
A = \text{Correct}
\]
Step 2: Check statement B.
Statement B is:
\[
\text{Only meritorious students will be considered for scholarship.}
\]
This is a simple categorical-type statement.
It does not combine two propositions by a logical connective.
So, B is not selected.
Step 3: Check statement C.
Statement C is:
\[
\text{Be neither a borrower nor a lender.}
\]
The expression neither...nor combines two negative ideas.
It means:
\[
\text{Do not be a borrower and do not be a lender.}
\]
So, C is a compound proposition.
\[
C = \text{Correct}
\]
Step 4: Check statement D.
Statement D is:
\[
\text{Two triangles are formed if a square is divided diagonally.}
\]
The word if makes it a conditional proposition.
It means:
\[
\text{If a square is divided diagonally, then two triangles are formed.}
\]
So, D is also a compound proposition.
\[
D = \text{Correct}
\]
Step 5: Check statement E.
Statement E is:
\[
\text{Not all good speakers are good writers.}
\]
This is a quantified negative statement.
It does not combine two separate propositions by a connective.
So, E is not selected.
Step 6: Final conclusion.
The compound propositions are:
\[
A,\ C,\ D
\]
Hence:
\[
\boxed{\text{(B) A, C and D only}}
\]