question: online shopping:surf
choices.label: A B C D
choices.text: reading:books drink water:boil water practice calligraphy:write sing:chant
explanation: the necessary condition for "online shopping" is to "surf", and "surf" is a verb. "reading" means reading paper books or e-books, so "books" are not a necessary condition for "reading". "drinking water" does not require "boiling water", and "boiling water" is not a necessary condition for "drinking water". the necessary condition for "practice calligraphy" is "write", and "write" is a verb. the necessary condition for "singing" is not "chanting", "singing" and "chanting" have similar meanings.
relation: online shopping surf R5.4
relation: reading books R3.10
relation: practice calligraphy write R5.4
relation: sing chant R1.1