An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well.
Answer:
deuterostomes
Explanation:
During the formation of the gastrula, a group of cells migrates towards the inside. The resultant sac forms the embryonic gut. The embryonic gut has an opening that opens to the outside and is called the blastopore. The blastopore may give rise to mouth or anus. In some organisms, blastopore develops into the anus. These organisms are called deuterostomes. The other organisms in which blastopore develops into the mouth are called protosomes. Echinoderms, hemichordates, and chordates are deuterostomes.
After two half-lives or 60 years, 7.5 g of the element will be left.
<u>Explanation:</u>
<u>Half-life:</u>
- In simple words, Half-life can be defined as the amount of time needed for a quantity to fall to half its value as contained at the beginning of the time period.
- In this problem the half-life of the element is thirty years, then after thirty years half of the sample would have decayed and half would be left as it is.
- After thirty years (The first half-life ) 30 /2 = 15 g declines and 15 g remains disappeared.
- And after another sixty years (The two half-lives) 15 /2 = 7.5 g declines and 7.5 g remains disappeared.
- After two half-lives or 60 years, 7.5 g of the element will be left.
They are equals in their own way and form
