2000004502

SubArea: 
Combinatorics
Level: 
A
Project ID: 
2000004502
Accepted: 
0
Clonable: 
0
Easy: 
1
Specify the number of all two-element subsets of the set \( \{A, B, C, D, E \}\).
\( {{5}\choose{2}} =10\)
\( \frac{5!}{2!} =30\)
\( \frac{5!}{3!} =20\)
\( 5\)