Final answer:
In structural wood framing, 'checking' refers to cracks along the wood grain caused by drying and shrinking, and is not usually worrisome unless the checks are large, deep, or accompanied by other damage signs.
Step-by-step explanation:
"Checking" in a structural wood framing member such as a wooden beam is caused by drying and shrinking of the wood and is usually not a cause for concern. This phenomenon typically appears as cracks that run along the grain of the wood. While checks are common as the wood adjusts to changes in moisture content and environment, they don't always compromise the structural integrity of the wood. Thus, the correct answer is C. It is important, however, to monitor the checks to ensure they do not grow or indicate underlying issues. Broad, deep checks, or those accompanied by other signs of distress, may warrant a closer inspection by a professional. If insects or decay contribute to these cracks, it is a different concern, which would be option D.