Explanation

The heart is a muscular organ about the size of a fist, located just behind and slightly left of the breastbone.

The heart pumps blood through the network of arteries and veins called the cardiovascular system.

Explanation

 When an object moves at constant speed, its acceleration is zero.  

According to Newton’s Second Law:  

F = ma → If a = 0, then F = 0

Explanation

 Cleavage is the tendency of a crystal to break along specific planes of weakness.

Copper, being a metal, has a unique atomic structure that doesn't exhibit distinct planes of weakness.

When stressed, it tends to deform rather than cleave, resulting in a jagged fracture. 

Explanation

 The maximum number of electrons in an atom is given by the formula:  

Total electrons = 2n²  

For n = 4:  

2(1² + 2² + 3² + 4²) = 2(1 + 4 + 9 + 16) = 2(30) = 60  

But this is a misunderstanding. Each shell holds:

- n=1: 2  

- n=2: 8  

- n=3: 18  

- n=4: 32  

So total = 2 + 8 + 18 + 32 = 60, but this is not per atom.  

If n = 4 is the maximum principal quantum number, then the 4th shell is being filled.  

The maximum number of electrons that can exist in the 4th shell is:  

2n² = 2(4)² = 32

Explanation

Orbital velocity is 1/√2 times escape velocity, derived from gravitational motion equations.

Explanation

A respiratory surface must have a good supply of blood. 

A respiratory surface needs to be thin, permeable, and have a large surface area to efficiently facilitate gas exchange.

However, the crucial aspect is the blood supply.

The proximity of blood capillaries to the respiratory surface allows for the rapid transfer of oxygen from the air to the blood and carbon dioxide from the blood to the air. 

Explanation

 The part of a cell responsible for protein synthesis is the Ribosomes. 

Ribosomes are the cellular structures where proteins are synthesized by translating mRNA into amino acid chains

Explanation

A crystal can only have one center of symmetry. 

A center of symmetry is a point within a crystal where, if a line is drawn through that point and extended an equal distance on the other side, it intersects an identical point on the crystal.

Since this is a single, specific point within the crystal, there can only be one center of symmetry per crystal. 

Explanation

 Grignard reagent (RMgX) reacts with aldehydes (other than formaldehyde) to form secondary alcohols after acid hydrolysis.  

- With formaldehyde, it gives primary alcohol.  

- With ketones, it gives tertiary alcohol.

Explanation

 Lead tetroxide (Pb₃O₄), also known as red lead, crystallizes in the monoclinic crystal system.