The largest unit is determined by converting all values to the same unit:

2TB = 2,000GB

100GB = 100GB

4,000MB = 4GB

50KB = 0.00005GB

Thus, 2TB is the largest. As described in the CompTIA ITF+ FC0-U71 Study Guide:

“Data storage capacity is measured using standard units such as KB, MB, GB, and TB, where 1TB = 1,000GB.”