Problem: Extract the answer to the question from the following context. Question: What is the difference between solid and liquid media? Context: In the laboratory, bacteria are usually grown using solid or liquid media. Solid growth media, such as agar plates, are used to isolate pure cultures of a bacterial strain. However, liquid growth media are used when measurement of growth or large volumes of cells are required. Growth in stirred liquid media occurs as an even cell suspension, making the cultures easy to divide and transfer, although isolating single bacteria from liquid media is difficult. The use of selective media (media with specific nutrients added or deficient, or with antibiotics added) can help identify specific organisms.

A: Solid growth media, such as agar plates, are used to isolate pure cultures of a bacterial strain. However, liquid growth media are used when measurement of growth or large volumes of cells are required


Problem: Extract the answer to the question from the following context. Question: What is the term for marriage only within your local ethnic group? Context: A 2006 study found Ashkenazi Jews to be a clear, homogeneous genetic subgroup. Strikingly, regardless of the place of origin, Ashkenazi Jews can be grouped in the same genetic cohort – that is, regardless of whether an Ashkenazi Jew's ancestors came from Poland, Russia, Hungary, Lithuania, or any other place with a historical Jewish population, they belong to the same ethnic group. The research demonstrates the endogamy of the Jewish population in Europe and lends further credence to the idea of Ashkenazi Jews as an ethnic group. Moreover, though intermarriage among Jews of Ashkenazi descent has become increasingly common, many Haredi Jews, particularly members of Hasidic or Hareidi sects, continue to marry exclusively fellow Ashkenazi Jews. This trend keeps Ashkenazi genes prevalent and also helps researchers further study the genes of Ashkenazi Jews with relative ease. It is noteworthy that these Haredi Jews often have extremely large families.

A: endogamy


Problem: Extract the answer to the question from the following context. Question: What does the rotor field communicate with? Context: A PM motor does not have a field winding on the stator frame, instead relying on PMs to provide the magnetic field against which the rotor field interacts to produce torque. Compensating windings in series with the armature may be used on large motors to improve commutation under load. Because this field is fixed, it cannot be adjusted for speed control. PM fields (stators) are convenient in miniature motors to eliminate the power consumption of the field winding. Most larger DC motors are of the "dynamo" type, which have stator windings. Historically, PMs could not be made to retain high flux if they were disassembled; field windings were more practical to obtain the needed amount of flux. However, large PMs are costly, as well as dangerous and difficult to assemble; this favors wound fields for large machines.

A: magnetic field


Problem: Extract the answer to the question from the following context. Question: What effect is displayed on a disc with 77 lines, spinning at 77.92 rpm, when exposed to 50 Hz light? Context: In 1925, 78.26 rpm was chosen as the standard because of the introduction of the electrically powered synchronous turntable motor. This motor ran at 3600 rpm, such that a 46:1 gear ratio would produce 78.26 rpm. In parts of the world that used 50 Hz current, the standard was 77.92 rpm (3,000 rpm with a 77:2 ratio), which was also the speed at which a strobe disc with 77 lines would "stand still" in 50 Hz light (92 lines for 60 Hz). After World War II these records were retroactively known as 78s, to distinguish them from other newer disc record formats. Earlier they were just called records, or when there was a need to distinguish them from cylinders, disc records.

A:
would "stand still"