The answer to question one is A.
The answer to question two is A.
The answer to question three is D.
Answer:
contains many young stars
Explanation:
Irregular galaxies have <em>no definite shape</em>, which means that the first option is incorrect. They are definitely not round.
However,<u> they contain many young stars because the degree of star formation is fast.</u> They also contain old stars. Thus, the second choice is correct.
The "spiral galaxy" is the type of galaxy that has arms that extend from the center. These arms look "spiral," which influenced its name. This makes the last choice incorrect.
They are actually <u>smaller than the other types of galaxies.</u> This makes them <em>prone to collisions</em>. This makes the last choice incorrect.
First we need to find the speed of the dolphin sound wave in the water. We can use the following relationship between frequency and wavelength of a wave:

where
v is the wave speed

its wavelength
f its frequency
Using

and

, we get

We know that the dolphin sound wave takes t=0.42 s to travel to the tuna and back to the dolphin. If we call L the distance between the tuna and the dolphin, the sound wave covers a distance of S=2 L in a time t=0.42 s, so we can write the basic relationship between space, time and velocity for a uniform motion as:

and since we know both v and t, we can find the distance L between the dolphin and the tuna:
Answer:
The slope of a graph of position vs time