The white round crunchy things in Chinese food are Water Chestnuts.
Water Chestnuts are bulbs, with a sweet, apple like flavor and a crisp texture, and they are often sliced or chopped and used in stir fries.
Other things that are white and crunchy in some Chinese foods are crispy rice noodles or Vermicelli, which are deep fried to a puffed and crunchy texture, and these white strands are used to add texture or as a base for saucy dishes.
Broccoli stems, are peeled and cut and these white parts offer a crunchy texture and are also common in restaurant stir-fries.
Another thing that can be white and crunchy in Chinese food are Daikon Radishes which are shredded and provides a crisp, slightly sharp crunch, often seen in Asian salads or even pickled.
And less common, Jicama, which is a root vegetable, with a crisp, apple like crunch and mild flavor and sometimes used in salads.
And Tang Yuan, (if sweet) are sweet glutinous rice balls that are served in dessert soups.
The most common white round crunchy things in Chinese food are Water Chestnuts.
Water Chestnuts are white, juicy and crunch, and stay crisp even when cooked, and are also popular in many Asian dishes.