In Civil 3D, you can use the Ctrl Key to alter the selection of certain objects. For example, if you select a single alignment geometry point label, the entire string of labels are selected. However if you hold the Ctrl key and select a single alignment label, only the label you pick is selected. This is useful if you want to delete a single label. The same thing applies to grade break labels on a profile.
Selection of one alignment label, entire string is selected.
Selection of one alignment label while using the Ctrl key, only that label is selected
If for some reason the Ctrl assisted selection method does not work, check the value LEGACYCTRLPICK. When this is set to 1, the Ctrl key has no effect when trying to select a single label.
Interestingly, as noted in the documentation on LEGACYCTRLPICK, the sysvar SUBOBJSELECTIONMODE has an effect on how selections are performed. When SUBOBJSELECTIONMODE is set to 2 or 3, single label selection is the default and the Ctrl key is not needed.