When hydrogen combines with oxygen in the presence of an electric current, the chemical reaction that takes place is known as electrolysis of water. This process can be broken down into two half-reactions: the oxidation of water and the reduction of water.

1. Oxidation of Water:
At the anode (positive electrode), the following reaction occurs:
2H2O(l) -> O2(g) + 4H+(aq) + 4e^-
Here, water molecules are being oxidized, resulting in the formation of oxygen gas (O2), hydrogen ions (H+), and electrons (e^-).

2. Reduction of Water:
At the cathode (negative electrode), the following reaction takes place:
4H2O(l) + 4e^- -> 2H2(g) + 4OH^-(aq)
In this half-reaction, water molecules are being reduced, leading to the formation of hydrogen gas (H2) and hydroxide ions (OH^-).

Overall Reaction:
Combining the two half-reactions, we get the overall reaction:
2H2O(l) -> 2H2(g) + O2(g)
This means that when hydrogen combines with oxygen in the presence of an electric current, water (H2O) is formed.

Explanation:
During electrolysis of water, the electric current provides the necessary energy to break the bonds between hydrogen and oxygen atoms in water molecules. The positive electrode (anode) attracts negatively charged ions (anions) such as hydroxide ions (OH^-), while the negative electrode (cathode) attracts positively charged ions (cations) like hydrogen ions (H+).

At the anode, water molecules lose electrons and are oxidized to form oxygen gas, hydrogen ions, and more electrons. Meanwhile, at the cathode, water molecules gain electrons and are reduced to form hydrogen gas and hydroxide ions. The overall result of the process is the separation of water into its constituent elements, hydrogen and oxygen.

So, the correct answer is option 'D' - H2O (water) is formed.