The correct answer is $\boxed{\text{A}}$.
A three-bit jumper block can be used to set the logical ID of a SCSI drive. The logical ID is a number that identifies the drive to the SCSI host adapter. The logical ID can be set by shorting or opening the jumpers on the jumper block.
To set the logical ID to 3, the first and third jumpers should be shorted, and the second jumper should be open. This can be represented in binary as 100.
Option $\text{B}$ is incorrect because it represents the logical ID 2. Option $\text{C}$ is incorrect because it represents the logical ID 1. Option $\text{D}$ is incorrect because it represents the logical ID 4. Option $\text{E}$ is incorrect because it is not a valid option.