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.
A homologous structures are structures that share an evolutionary  ancestry. An example of homologous structures would be the bones in  the arms of a human, the wings of a b â¦ at, and the legs of a dog.hese structures may serve the same or different functions. For example, the wing of a bird and the arm of a human serve very different functions, but are considered homologous structures because of the evolutionary relationship between birds and humans.