I am not sure what this is
Answer:

Explanation:
As we know by radioactivity law

so here we will have


now we will have


now we also know that



Answer:Arctic circle
Explanation:
Arctic circle is one of the circles of latitude. It is located at the northern region if the equator and passes through more than one continent. These continent includes: North Asia,
Northern America, and
Europe.
In these continent, it passes through eight known counties. These countries includes: Canada, Russia, Norway, Sweden, Finland, Denmark, Alaska and Iceland. It covers 4% of the Earth surface and it's climatic conditions are extreme.
The answer that best fits the blank is the term WAXING. The moon is waxing whenever it reaches to the period that its phases are transitioning from new to full. The answer is the first option. This is when it is more that half is illuminated. Hope this helps.
the answer is spiral galaxies