Step 1: Compute the first differences of the given terms 2, 6, 12, 20, 30: $6-2=4$, $12-6=6$, $20-12=8$, $30-20=10$. These differences themselves increase by a constant 2 each time (a second difference of 2), so the next first-difference should be 12.
Step 2: Rather than just adding, verify by testing each option and checking whether it keeps the second difference constant at 2.
Step 3: Test option "40": difference would be $40-30=10$, same as the previous difference, giving a second difference of $10-10=0 \ne 2$. Reject.
Step 4: Test option "44": difference would be $44-30=14$, giving a second difference of $14-10=4 \ne 2$. Reject.
Step 5: Test option "38": difference would be $38-30=8$, giving a second difference of $8-10=-2 \ne 2$. Reject.
Step 6: Test option "42": difference is $42-30=12$, giving a second difference of $12-10=2$, which matches the constant pattern perfectly.
\[\boxed{42}\]