问题详情

Why does the professor discuss the presence of zinc in paint pigments？

A．To explain why some paints may deteriorate over the course of time

B．To stress the need for caution when attempting to restore old artworks

C．To show how pigments differ from varnishes and binding agents

D．To show how spectroscopy can help establish the age of a painting

此题为多项选择题。请帮忙给出正确答案和分析，谢谢！