Which of the following is the natural source of lactic acid?

I. 6x² + 37x + 45 = 0

II. 3y² - 11y + 6 = 0

I. x² - 19x + 84 = 0

II. y² - 25y + 156 = 0

I. 4 x ² - 4 x + 1 = 0

II. 4 y ² + 4 y + 1 = 0

I. 8x²- 2x – 15 = 0

II. 12y²- 17y – 40 = 0

I. 3y² - 20y + 25 = 0

II. 3x² - 8x + 5 = 0

I.  2^(x+2)+ 2^(-x)=5

II.  (1/(y+1)+ 1/(y+5))=(1/(y+2)+  1/(y+4))

I. 2x² - 9 x + 9 = 0 

II. 2y² - 7 y + 3 = 0

I. x² - 9x - 52 = 0

II. y² - 16y + 63 = 0

I. 15b²+ 26b + 8 = 0

II. 20a²+ 7a - 6 = 0

I. 12x² + 22x + 8 = 0

II. 4y² - y − 3 = 0