(February 2013) Durham tubes are used in microbiology to detect production of gas by microorganisms. They are simply smaller test tubes inserted upside down in another test tube. This small tube is initially filled with the solution in which the microorganism is to be grown.
A compound predicate is two or more simple predicates joined by a conjunction that indicate actions by the same subject. Example : Bill picked up the mail and walked the dog.. Bill is the subject for both verbs.
To determine whether a group of words is a phrase or a clause, you must be able to find the subject and predicate. (Predicate is another term for a verb.). The subject is the part of a sentence that tells who or what the sentence is about. To find the subject, ask who or what is doing something. The predicate is the part of a sentence that asserts something about the subject.