Step 1: Understanding the Concept
Coins of the same denomination are identical, so we count arrangements of a multiset.
Step 2: Total arrangements
There are 9 coins: 4, 3 and 2 of three kinds. The total number of stackings is \(\dfrac{9!}{4!\,3!\,2!}=1260\).
Step 3: Favourable arrangements
Each denomination forms one block, so we arrange 3 blocks in \(3!=6\) ways.
Step 4: Probability
\(P=\dfrac{6}{1260}=\dfrac{1}{210}\)
Final Answer:
The probability is 1/210.
\[ \boxed{\text{(B) }\dfrac{1}{210}} \]