Nouns used in singular and plural. Which phrase is correct - the class was or the class were? Is the word class a singular noun or a plural noun? This question cannot be answered with Yes or No. Use the singular if you see the class as a group of students. Use the plural if you see the class as single students. In British English the plural is used more often than in American English. There are more words which can be singular or plural nouns: army.
In much of a digestive tract such as the human gastrointestinal tract, smooth muscle tissue contracts in sequence to produce a peristaltic wave, which propels a ball of food (called a bolus while in the esophagus and upper gastrointestinal tract and chyme in the stomach) along the tract. The primary peristaltic wave forces the bolus down the esophagus and into the stomach in a wave lasting about 8â9 seconds. 2  The wave travels down to the stomach even if the bolus of food descends at a greater rate than the wave itself, and continues even if for some reason the bolus gets stuck further up the esophagus.
a. wave. b. medium. c. vibration. d. compression. ____ 30. The highest parts of a transverse wave are called. a. troughs. b. crests. c. nodes. d. wavelengths. ____ 31. Waves that move the particles of the medium parallel to the direction in which the waves are traveling are called. a. longitudinal waves. b. transverse waves. c. surface waves. d. combination waves. ____ 32. The distance between two corresponding parts of a wave is the waveâs. a. amplitude. b. wavelength. c. frequency. d. speed. ____ 33. The bending of waves due to a change in speed is called. a. reflection. b. refraction. c. diffraction. d. interference. ____ 34. The bending of waves around the edge of a barrier is known as. a. reflection. b. refraction. c. diffraction. d. interference. ____ 35. Waves produced by earthquakes are called. a. standing waves. b. transverse waves. c. seismic waves. d. longitudinal waves. ____ 36. Longitudinal seismic waves are known as. a. primary waves. b. secondary waves. c. surface waves. d. transverse waves. ____ 37.