How many moles of water can be produced?

2H₂ + O₂ → 2H₂O
OR: Mole ratio O₂ : H₂O = 1 : 2

No. of moles of O₂ reacted = 13.58 mol
No. of moles of H₂O produced = (13.58 mol) × 2 = 27.16 mol ≈ 27 mol (2 sig. fig.)

...... Answer : a. 27

As you have given the balanced equation
2H2 + O2 = 2H2O
Note the molar ratios are 2:1::2

Hence
13.58 mol(O2) is equivalent to '1' in the molar ratios.
Hence
13.58 X 2 = 27.16 mol(H2O) is equivalent to '2' in the molar ratios.

Hence from the optional answers, answer 'a' 27 moles.