Use M x V = M' x V'
0.300 x V = 0.100 x 250
V = .......... ml
Answer: The correct option is 3.
Explanation: We are given a compound which is made up of iron and oxygen only. The ratio of the two are given as:

This means that, number of iron ions are 2
Number of oxide ions are 3
From the above information, the formula becomes : 
The valency of iron = 3
Valency of oxide = 2
This compound is named as iron (III) oxide.
Hence, the correct option is 3
Answer:
Pitch:it refers to the highest and lowness of a sound.
Wavelength: It is the distance measured from one crest to another, or from one trough to another.
Refraction of Light: The light bends as it travels from one medium to another.
Reflection of Light: It happens when light bounces back after hitting a well-polished surface.
Crest: The highest point of the wave from the center.
<u>I hope this helps! :)</u>