Under the UCC, a(n) is a sequence of previous conduct between the parties to an agreement which may be fairly regarded as establishing a common basis of understanding for interpreting their conduct under the contract.

a. course of dealing
b. usage of trade
c. course of performance
d. integrated document.

a.  course of dealing

Explanation:

Under UCC which is an acronym for Uniform Commercial Code, "a course of dealing" as explained in the subsection 1-303(b) is a term that describes or explains the sequence of conduct concerning previous transactions between the parties to a particular transaction that is fairly to be regarded as establishing a common basis of understanding for interpreting their expressions and other conduct.

It is often used to explain or further give credence to written contract, such that, in a court of law, it is used to assess the position of parties to the the contract, this tends to understand what the parties to contract seek to achieve, based on their previous dealings on transaction.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.