This statment is false, the pen on a seismograph does not swing freely.
Solutions are said to be C. homogeneous mixtures, composed of two or more substances. It is usually liquid, however it may be solid or gas.
Answer: The volume of 
required is 25.0 ml
Explanation:
According to the neutralization law,
where,
= basicity 
= 1
= molarity of solution = 2.00 M
= volume of solution = 50.0 ml
= acidity of = 1
= molarity of solution = 4.00 M
= volume of solution = ?
Putting in the values we get:
Therefore, volume of required is 25.0 ml
