◎◎◎ cave ⪢⪢
A _____ is a natural opening in the ground with a hollow space beneath the surface large enough for people to enter.
http://qindex.info/i.php?x=1182

◎◎◎ landform ⪢⪢
_____s are natural features of the earth's surface like mountains, deserts and plains.
http://qindex.info/i.php?x=23826

○○○ testament ⪢⪢
The beautiful performance was a _____ to the singer's natural talents. #bookmark
http://qindex.info/i.php?x=18754

○○○ Charles Darwin ⪢⪢
Charles Darwin made what might be the most important scientific discovery of all time, the theory of evolution by natural selection.
http://qindex.info/i.php?x=12925

○○○ government ⪢⪢
European Union governments approve a plan to limit natural gas use during the winter to protect against further supply cuts by Russia. 2022-07-26
http://qindex.info/i.php?x=21604

○○○ Taixing ⪢⪢
A new 750-kilometer-long part of the Russia-China natural gas pipeline opens, connecting Siberia to Taixing on the Yangtze River. 2022-12-07
http://qindex.info/i.php?x=23684

○○○ Cappadocia ⪢⪢
In central Turkey, _____ is a scene straight out of a fairy tale combining both natural and man-made beauty. #place
http://qindex.info/i.php?x=24068

○○○ unparalleled ⪢⪢
The sense of wonder and awe that awaits those who make this journey is _____ making Mach Picchu an essential destination for anyone with a passion for history, archeology and the sheer beauty of the natural world. #bookmark
http://qindex.info/i.php?x=28294

○○○ barrier ⪢⪢
The Rhodope and Pindus mountains form natural _____s with its northern neighbors. #Greece
http://qindex.info/i.php?x=29089

○○○ man-made ⪢⪢
Although it seems a natural wonder, it is actually _____ .
http://qindex.info/i.php?x=28487

• prime number theorem
○ Around 300 BC Euclid proved there were infinite number of prime numbers. ○ The number of prime numbers less than a certain natural number is asymptotically equivalent to x/(x⍻e).
http://qindex.info/i.php?x=3779

• 42 Logarithms Part 2
Base Ten Logs, Natural Logs, and the Change-Of-Base Property
http://qindex.info/i.php?x=3639

• On The Origin Of Species
How do we explain how animals have evolved over time. Charles Darwin, the British naturalist and geologist, famously answered this question in his book 'On The Origin Of Species' which proposed the mechanism of evolutionary change within animal species.
http://qindex.info/i.php?x=4766

• 42 Logarithms Part 2
Base Ten Logs, Natural Logs, and the Change-Of-Base Property
http://qindex.info/i.php?x=5041

• Introduction to Minerals
○ 5 citeria: solid, naturally occurring, inorganic, fixed chemical formula, specific atomic arrangement -- igneous, granite, speckle, quartz, biotite mica, plagioclase feldspar, fluorite, talc, selenite gypsum, pyrite, silicate, bituminous, sulfur, halite
http://qindex.info/i.php?x=4013

• Mathematical Induction
Let P(n) be a statement for each natural number n. If (a) P(1) is true, and (b) P(k) true ⇒ P(k+1) true for every natural number k∈ℕ then P(n) is true for all n∈ℕ.
http://qindex.info/i.php?x=9716

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