From the line graph, we can extract the total number of units shipped for the months of January, February, and March:
- Units shipped in January: 15,000
- Units shipped in February: 20,000
- Units shipped in March: 20,000
Now, sum these values:
\[
\text{Total Units Shipped} = 15,000 + 20,000 + 20,000 = 55,000
\]
Thus, the correct answer is (B).