Answer
**Humor:** In its appraisal of Upton Sinclair, Time magazine suggested a conspicuous absence of humor in his character. This deficiency manifested itself both personally and in his literary works, often characterized by a solemnity that bordered on humorlessness. This trait stood in stark contrast to his contemporary writers known for their wit and satirical touch. As a result, Sinclair's lack of humor became a distinguishing feature attributed to him.