The furniture __________ very expensive.

The correct answer is "is" because "furniture" is an uncountable noun in English. Uncountable nouns, also known as mass nouns, refer to things that cannot be counted individually and do not have a plural form. Despite referring to multiple items like chairs, tables, and desks, the word "furniture" itself is treated as a singular entity. Therefore, it always requires a singular verb.

Consider other common uncountable nouns that follow this rule:

• "Information" (e.g., The information is helpful.)
• "Advice" (e.g., Her advice is valuable.)
• "Equipment" (e.g., The equipment is new.)
• "News" (e.g., The news is shocking.)

In these cases, even if the concept implies multiple pieces or facts, the noun itself remains singular in form and takes a singular verb. Hence, "The furniture is very expensive" correctly applies the rule of subject-verb agreement for uncountable nouns.