2.1 kg of sodium bicarbonate is equal to the 2.1 x 10¹² ng of sample. Option D is correct.
Mass is the quantity of the substance in the body or object. The SI unit of mass is Kilogram.
There are other units of measure,
- Milligram: 1 g is equal to the

- Micro-gram: 1 g is equal to

- Nano-gram: 1 g is is equal to
First convert kg to gram,
Since, 1 Kg = 1000 g
2.1 kg = grams of sample
So,
Do the cross multiplication,

Now, convert 2100 g to nano-grams
Since, 1 g = 1 x 10⁹ ng
2100 g = ng of sample
So,
Do the cross multiplication,

Therefore, 2.1 kg of sodium bicarbonate is equal to the 2.1 x 10¹² ng of sample.
To know more about Mass units,
brainly.com/question/489186
Answer:
The epicenter is the point on the earth's surface vertically above the hypocenter (or focus), point in the crust where a seismic rupture begins.
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All that business about the crane and the rope and the falling
is only there to confuse us.
The piano ended up 5 meters above the ground.
Potential energy = (mass) (gravity) (height)
= (200 kg) (9.81 m/s²) (5 m)
= (200 · 9.81 · 5) (kg-m²/s²)
= 9,810 joules .
Direction of prevailing winds. shape of the land (known as 'relief' or 'topography') distance from the equator. the El Niño phenomenon.
Answer:A
Explanation:
Given
Two ponies are at Extreme end of turntable with mass m
suppose turntable is moving with angular velocity 
Moment of inertia of Turntable and two ponies

let say at any time t they are at a distance of r from center such 
Moment of inertia at that instant


conserving angular momentum as net Torque is zero



Thus we can say that angular velocity increases as they move towards each other.