Observing is commenting on what you see e.g: It is raining.
Inferring is drawing conclusions from observations for example you see the road is wet so you might infer that it rained last night.
Answer:
"Crust" refers to a
terrestrial planet's outermost surface.
In general, the Earth's crust is divided into
older, thicker continental crust and younger, denser oceanic crust.
...
The thin, 40-kilometer (25-mile) deep crust of our planet — just
1 per cent of Earth's mass — contains all known universe existence.
Explanation:
Continental crust is thicker, 22 miles (35 km) on average and less dense than oceanic crust, which accounts for its mean surface elevation of about 3 miles (4.8 km) above that of the ocean floor (Archimedes’ principle). Continental crust is more complex than oceanic crust…
1) Frequency: 
The frequency of electromagnetic radiation is given by:
where
is the speed of light
is the wavelength
In this case, the wavelength of the radiation is
Therefore the frequency is
2) Period: 
The period is equal to the reciprocal of the frequency of the wave:
Using the frequency we found previously, 
, we find:
<span>All organisms need an
environment that will allow them to reproduce. Now, that can mean lots
of things. Humans for instance, need a place where they will find food,
water and sun light. They will also need shelter in order to be able to
protect their babies. But bacteria for example, they can live literally
anywhere. They live in places as acidic as our stomachs, as hot as
volcanoes, and as cold as ice in the poles.</span>
