The Select Features tool selects every feature in a feature class, if one feature is selected when the data frame is in a geographic coordinate system or is undefined, and the display units are set to UTM, MGRS, or U.S. National Grid in the Data Frame Properties.
1. Set the display units from the Data Frame Properties to any unit other than UTM, MGRS, or US National Grid.2. Go to Customize > ArcMap Options > Data View tab > Check the 'Use these units instead of data frame's Display units' checkbox and select UTM, MGRS, or U.S. National Grid > Click OK. The feature can now be selected one at a time.