Many things make people think artists are weird—the odd hours, the nonconformity, the clove cigarettes. However, the weirdest may be this: artists’ only jobs are to explore emotions, and yet they choose to focus on the ones that feel lousy. This wasn’t always so. The earliest forms of art, like painting and music, are those best suited for expressing joy. But somewhere in the 19th(上标) century, more artists began seeing happiness as insipid, phony or, worst of all, boring. In the 20th(上标) century, classical music became more atonal, visual art more unsettling. Sure, there have been exceptions, but it would not be a stretch to say that for the past century or so, serious art has been at war with happiness. In 1824, Beethoven completed his "Ode to Joy". In 1962, novelist Anthoy Burgess used it in A Clockwork Orange as the favorite music of his ultra-violent antihero. You could argue that art became more skeptical of happiness because modern times have seen such misery. But the reason may actually be just the opposite: there is too much damn happiness in the world today. In the West, before mass communication and literacy, the most powerful mass medium was the church, which reminded worshippers that their souls were in peril and that they would someday be meat for worms. Today the messages that the average Westerner is bombarded with are not religious but commercial, and relentlessly happy. Since these messages have an agenda—to prey our wallets from our pockets—they make the very idea of happiness seem bogus(假的). "Celebrate!" commanded the ads for the arthritis drug Celebrex, before we found out it could increase the risk of heart attack. What we forget—what our economy depends on us forgetting—is that happiness is more than pleasure without pain. The things that bring the greatest joy carry the greatest potential for loss and disappointment. Today, surrounded by promises of easy happiness, we need someone to tell us that it is OK not to be happy, that sadness makes happiness deeper. As the wine-connoisseur movie Sideways tells us, it is the kiss of decay and mortality that makes grape juice into Pinot Norway need art to tell us, as religion once did, that you will die, that everything ends, and that happiness comes not in denying this but in living with it. It’s a message even more bitter than a clove cigarette, yet, somehow, is a breath of fresh air. What does the author mean by "a stretch"

A terrible thing.
B. An exaggeration.
C. A continuous period of time.
D. An exception.