Correct option is A
The error in "These equipments must have cost a fortune" is found in part A.
• "Equipment" is an uncountable noun and does not have a plural form.
• Therefore, "equipments" should be corrected to "equipment" to accurately reflect its uncountable nature.
• The corrected sentence should be "This equipment must have cost a fortune," properly using "equipment" in its singular (and only) form.
• Uncountable nouns are nouns that cannot be counted and do not typically have plural forms.