When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n) When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n) regulon. operator. autoinducer. riboswitch.

Regulon

Explanation:

A regulon comprises of a group of operons that are controlled by the same regulatory protein referred to as a regulator which could act as a repressor or activator.

Regulons in bacterial cells are referred to as the fundamental unit of the response system. Regulons are majorly used when referring to prokaryotes that have their genome organized to operons, although this term is not limited to that. The genes that are found in a regulon are arranged into two or more operons at different regions on the chromosome.

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.