Number Properties: Analyzing the Sequence 1,2,3,4,5,6

To solve this problem, we need to determine if there's a consistent pattern or rule in the sequence $1, 2, 3, 4, 5, 6$.

Let's proceed step by step:

• Step 1: Analyze the given sequence
  The sequence is $1, 2, 3, 4, 5, 6$.
• Step 2: Check for a common difference
  Calculate the difference between each consecutive pair of numbers:

$2 - 1 = 1$
$3 - 2 = 1$
$4 - 3 = 1$
$5 - 4 = 1$
$6 - 5 = 1$

From the calculations above, we observe that the difference between each consecutive term is $+1$.

Conclusion: The sequence is an arithmetic sequence with a common difference of $+1$.

Therefore, the correct choice is $+1$.