Answer:
to watered our source of food
the "PLANTS & TREES"
The possible structures with 6-C Chain and 1 double bond i.e. the isomers are 2-methylhex-2-ene , 3-methylhex-2-ene , 4-methylhex-2-ene , 5-methylhex-2-ene , 2-methylhex-3-ene , 3-methylhex-3-ene , 4-methylhex-3-ene , 5-methylhex-3-ene , 2-methylhexene , 3-methylhexene , 4-methylhexene , 5-methylhexene .2-methylene hexane , 3-methylenehexane .
These all are functional group isomers.
<h3>isomers :</h3>
same molecular formula but different physical and chemical properties .
<h3>Positional isomers :</h3>
same molecular and chemical formula but different in position of the functional group .it is a structural isomerism .
<h3>functional isomers :</h3>
same molecular formula but different functional groups attached to the main ring.
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The research of astronomy during the time period of 1970 - 1990 is given below:
<u>Date</u> <u>Event</u>
1. 15 June 1974 Black Brant VC sounding rocket from White Sands.
2. 14 May 1973 Launch of Skylab, the USA's first space station
3. 26 July 1971 Launch of Apollo 15
<h3>What is Astronomy?</h3>
This refers to the branch of science that deals with celestial bodies and their relation to each other.
Hence, from information about astronomy, between the time period 1970 - 1990 as it was on the 26th of December, 1974 that the Soviet space station Salyut-4 was launched.
The event I think had the greatest impact in astronomical history during this time period was the launch of Apollo 16.
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I believe the correct answer would be the first option. It is 100 mL graduated cylinder that is the best apparatus that could be used. It has the smallest graduation as compared to the other choices. It can measure up to 0.1 mL.