Answer:
A) actin and myosin is a correct answer.
Explanation:
- Myofibrils are the contractile fiber and they are made of actin and myosin.
- Myofibrils are made of thick myofilaments and thin myofilaments.
- Thick myofilaments are made up of myosin whereas thin myofilaments are composed of actin.
- The functional unit of muscle is Myofibrils and contraction of muscle occurs due to myofibril, when the filaments actin and myosin interact with each other.
Thus Myofibrils are made primarily of (A) actin and myosin.
Answer:
Normal force, gravity and Friction.
Explanation:
The forces acting on the book are normal formal force which act or exerts by the table on the book while on the other hand, gravity is a force that acts in the downward direction. Friction is the force that acts against the motion of the book and is responsible for lowering speed of the book that is sliding on the surface of the table. If the friction is low between the book and table then the book moves easily on the surface.
<h2>Fixation</h2>
Nitrogen in its gaseous form (N2) can’t be used by most living things. It has to be converted or ‘fixed’ to a more usable form through a process called fixation. There are three ways nitrogen can be fixed to be useful for living things:
<h3>Biologically: </h3>
Nitrogen gas (N2) diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+), which can be used by plants. Legumes (such as clover and lupins) are often grown by farmers because they have nodules on their roots that contain nitrogen-fixing bacteria.
<h3>Through lightning: </h3>
Lightning converts atmospheric nitrogen into ammonia and nitrate (NO3) that enter soil with rainfall.
Answer:
They are veins and arteries. The primary function of arteries is to transport highly oxygenated, nutrient-rich blood from our hearts and distribute it to the rest of our body. Veins, on the other hand, are used to pump much-needed blood back to the heart.