There are C(29, 4) = 29!/(4! (29 - 4)!) ways of selecting any 4 students from the total 21 + 8 = 29 students.
The teacher has C(21, 2) = 21!/(2! (21 - 2)!) ways of picking out 2 sophomores and C(8, 2) = 8!/(2! (8 - 2)!) ways of picking out 2 freshmen, so there are
C(21, 2) • C(8, 2) = 5880
possible ways of picking out 2 sophomore and 2 freshmen.
The probability of picking out a group of students like this is then
C(21, 2) • C(8, 2) / C(29, 4) = 280/1131 ≈ 0.2476
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A & B;
Article II of the U.S. Constitution lays out the framework for the executive branch.
Option C would be found in Article I, dealing with Congress. Option D would be found in Article III, dealing with federal courts. Let me know if you have further questions.
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Photoreceptors are responsible for visual phototransduction. They convert light into biological signals. In humans, rods, cone, and retinal ganglion cells are the 3 main photoreceptors.
Rods are narrow and are present throughout the retina. They are very sensitive, They can be triggered by a single photon also. They are responsible for the visuals we get in the low-light conditions.
Cons need a high number of photons, in order to produce signals. They are responsible for visualization of colors.
Rhodopsin is the pigment molecule of the rod cells. It is very sensitive to the light, and enables visualization in dim lights.
