The mass number of a nucleus (except Hydrogen) is: number of protons + number of neutrons.
A=Z+N
A=mass number=protons + neutrons.
Z=atomic number=number of protons.
N=number of neutrons.
In the case of Hydrogen it depends of isotope of Hydrogen .
the hydrogen has three isotopes,
protium : A=Z, because N=0
deuterium: A=Z+N; N=1
tritium: A=Z+N; N=2
It's because of the position of tectonic plates.
The skin is NOT a reproductive organ and the spines attract predators are the incorrect statements.
<h3>Why the list is incorrect?</h3>
The list is incorrect because skin is not a reproductive organ and the spines do not attract predators towards each other. Skin protects the body from the outer environment whereas the spines repel the predators from the plant body.
So we can conclude that the skin is NOT a reproductive organ and the spines attract predators are the incorrect statements.
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In other words, it would take Deep Space 1 more than 81,000 years to travel the 4.24 light-years between Earth and Proxima Centauri at its top speed of 56,000 km/h. In relation to human history, that would be more than 2,700 generations.
Nearly 40 trillion kilometers, or 4.4 light-years, separate us from Alpha Centauri. The NASA-Germany Helios probes, the fastest spacecraft to date to be launched into orbit, flew at a speed of 250,000 kilometers per hour. The probes would need 18,000 years to travel at such pace to arrive at the sun's nearest neighbor. The calculations reveal that it is almost impossible to reach the nearest star in a human lifetime, even with the most futuristic technologies.
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15+3=18km/hour
Think about it like this. The boat is going 15 faster than the river, and the river is going 3 faster than the bank, so the boat is going 18 faster than the river bank
