Yes. The group {0,1} has precisely 4 subgroups.
Carbon
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There are four distinct levels of protein structure. The main two are primary, amino acid, secondary structure, and quaternary structure.
Rulers, Tape Measures, Calipers, and Opisometers.
The four main groups are... Group O+ (the commonest), group A+, group B+ and group AB+
Rulers, Tape Measures, Calipers, and Opisometers.
A group of four singers is also known as a quartet.
Four Points Media Group was created in 2007.
Four Points Media Group ended in 2012.
There were not really subgroups in the historic or present Navajo people. At least not the way that the Lakota had 7 bands such as Hunkpapa or Oglala. Nor was it like the way Scottish clans ruled various territories. The Navajo have about 84 clans placed in 21 relationship groups. All are supposed to have come from the four original clans. However, because it is considered very wrong to marry anyone in any of the four clans of your grandparents, the clans are always getting mixed up over time. For traditional people, one should not even date or go to a dance with someone in one of the four clans of your grandparents. Certain clans are more common in different areas but they don't constitute subgroups.
the answer is iron
The noun for a four person singing group or musicians is a quartet.