本题考查美国文化的发展。

The United States has often been thought of as a melting pot, but beginning in the late 1990s and early 2000s. It trends towards cultural diversity, pluralism and the image of a salad bowl instead.

美国通常被认为是一个大熔炉，但从20世纪90年代末到21世纪初开始，它的发展趋势呈文化多样化和多元化，取而代之的是沙拉碗的形象。

故选择选项。