Step 1:
Say's Law states:
\[
\text{Supply creates its own demand}
\]
Step 2:
Assumptions include:
• Perfect competition
• Optimum allocation of resources
• Savings are automatically invested
Step 3:
• Market size can expand $\Rightarrow$ A is incorrect
• Labour and capital can adjust through price mechanism $\Rightarrow$ D is incorrect
Step 4:
Correct assumptions are:
\[
B,\; C,\; E
\]
Hence, the correct answer is:
\[
\boxed{\text{(3) B, C and E only}}
\]