The most commonly used diagnostic tool for tuberculosis is a simple skin test, though blood tests are becoming more commonplace. A small amount of a substance called PPD tuberculin is injected just below the skin of your inside forearm. You should feel only a slight needle prick.
The structure has a double bond and an adjacent atom with a lone pair, so it could have resonance. The possible resonance structures are below. The first structure has the most common bonding pattern for all of its atoms, so it is a reasonable Lewis structure.
Resonance Structures and the Resonance Hybrid. Resonance is possible whenever a Lewis structure has a multiple bond and an adjacent atom with at least one lone pair. The following is the general form for resonance in a structure of this type. The arrows show how you can think of the electrons shifting as one resonance structure changes to another.