The four classes of polymers are:
1. Nucleic acids. Examples are DNA and RNA
2. Protein. Examples are enzymes and hemoglobin
3. Carbohydrates. Examples as starch and glycogen
4. Lipids. Examples are triglycerides and phospholipids
The building blocks of nucleic acids are called bases and there are four types known as Guanine, Adenine, Thymine and Cytosine.
The building blocks of carbohydrates are glucose molecules.
The building blocks of protein are amino acids.
The building blocks of lipids are a combination of fatty acids and glycerol.

- c. The weight of an object on the moon will be the same as its weight on Earth. It is false because the weight of an on the moon will be 1/6 th times its weight on Earth.
- d. The weight of an object is its mass multiplied by the force of gravity. The statement is false because the formula of weight is mass × acceleration due to gravity, not force of gravity.
- e. The mass and weight of an object are the same thing. The statement is false because mass means a body of matter. While weight of an object is its mass multiplied by the force of gravity.
- f. The mass of an object is the force of gravity acting upon an object. It is false because it will be the weight of the object not mass.
- So, the answers are c, d, e and f.
Hope you could understand.
If you have any query, feel free to ask.
Gap junctions in the intercalated discs allow impulses to be spread across the heart more quickly. This is because gap junctions allow particles/signals to pass through, thus making cells with gap junctions more able to interact.
One more thing—you posted this in the physics section rather than biology.
Missing question: "What is the spring's constant?"
Solution:
The object of mass m=6.89 kg exerts a force on the spring equal to its weight:

When the object is attached to the spring, the displacement of the spring with respect to its equilibrium position is

And by using Hook's law, we can find the constant of the spring:
200 Hz = 200 cycles per sec
<span>1 cycle, the period = 1/200 = 0.005 seconds, or 5 milli seconds.</span>