Which compound can be refluxed with acidified potassium dichromate(VI) to form an organic product with molecular formula C4H6O2\text{C}_4\text{H}_6\text{O}_2C4H6O2?
butane-1,4-diol
3-hydroxybutanal
butane-2,3-diol
2-methylpropane-1,2-diol
