Art, Bob, Cab, and Ida are guards in a museum.

It is known that:

 Each of Art, Bob, and Cab stands guard on exactly four days every week.
 Exactly two persons stand guard together every day.
 No person stands guard three days in a row.
 Here is a partial listing that shows when they stand guard every week:

+-----+-----+-----+
| Sun | Art | Bob |
+-----+-----+-----+
| Mon | Cab |  ?  |
+-----+-----+-----+
| Tues| Ida |  ?  |
+-----+-----+-----+
| Wed | Art |  ?  |
+-----+-----+-----+
|Thurs| Bob |  ?  |
+-----+-----+-----+
| Fri | Cab |  ?  |
+-----+-----+-----+
| Sat | Ida |  ?  |
+-----+-----+-----+

Who does NOT stand guard with Ida?