In an aqueous solution which substance yields hydrogen ions as the only positive ion *

The question is incomplete. Complete question is
In an aqueus solution, which substance yields hydrogen ions as the only positive ions in the solution? 1)NaH 2)HCOOH 3)LiOH 4) CH3CH2OH?

Correct answer is option 2, HCOOH

Reason: 
HCOOH is a formic acid. When mixed in water, it undergoes dissociation which can be represented as

HCOOH         ↔           HCOO-       +            H+

The compound NaH, will generate hydride ion (H-), while LiOH is an ionic compound, hence when dissolved in water it generated OH- ions. The compound CH3CH2OH is named as ethyl alcohol. This compound donot dissociate in aqueous medium. 

Ci think not

True, the standard unit for volume is liters which can be represented by either a lower case "l" or a capital "l"