They are called stem cells. This cells are undifferentiated which means it can specialize in other types when it receives the right stimuli. They can divide through mitoses and become more stem cell or become a bone, muscle, blood cell, etc.
They can have 2 origins: embryos or some human tissue; their function is to regenerate or substitute damaged cells
The answer to your question is "A. a lower frequency of the siren.
Because the person in back of the ambulance will hear a lower frequency of the siren. This is because the waves are stretched out. A longer wavelength results in a lower frequency.
The answer is
Pitch of the buzzer increased (higher tone) as it moves towards the observer
Answer:

It will float.
Explanation:
Hello.
In this case, given the width, length and height, we can compute the volume as follows:

Moreover, since the density is computed via the division of the mass by the volume:

We obtain:

In such a way, since the solid has a lower density than the water, we infer it will float.
Best regards.
Answer:
11 m/s south
Explanation:
The velocity of the passenger relative to the river bank is equal to the velocity of the passenger relative to the ferry, plus the velocity of the ferry relative to the river, plus the velocity of the river relative to the river bank.
v_passenger,bank = v_passenger,ferry + v_ferry,river + v_river,bank
If we take north to be positive and south to be negative:
v = 1.0 m/s + (-10 m/s) + (-2 m/s)
v = -11 m/s
v = 11 m/s south