Answer:

Explanation:
Given that
Train 1 (observer):
Speed = 109 km/h
Train 2 (source):
Speed = 99 km/h
Train 2 emitting frequency = 500 Hz
We know that observer and source are moving toward each other, then frequency heard by observer can be given as follows

Where C is the velocity of sound (C=1225 Km/h)
Now by putting the values



ANSWER:
IV, Type of dish detergent. DV, height of foam. CV, type of container, amount of water in container, temperature of water, time the container is agitated.
Explanation:
Independent variable(IV)- what you change during the experiment.
dependent variable(DV)- what you're measuring during an experiment. The dependent variable is DEPENDENT because it's results DEPEND on the independent variable at play.
Constant variables(CV)- things that do not change in order to isolate the tested variables as much as possible.
Answer:
I think it's D!!
cuz protons are in the atoms