Answered

Which of these follows a cyclical pattern?
A. sunspot maxima and minima
B. condensation of a nebula
C. formation of a crater
D. formation of a black hole

Sagot :

AL2006id
The number of sunspots, observed during the past 300 years or so,
has been found to vary up and down in a cycle of very very roughly 
about 11 years.

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