(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.
When a sentence has more than one subject per verb, those subjects form a compound subject. Compound subjects can be singular, plural, or a mix of both: TWO SINGULAR: The dog and the cat bother me. TWO PLURAL: The dogs and the cats bother me. ONE SINGULAR, ONE PLURAL: The dog and cats bother me.