`Hand-in-Hand 2007` was a joint anti-terrorism military training operated by the officers of the Indian Army alongside officers of another nation`s army. The objective of such exercises is to improve cooperation, understanding, and readiness to combat terrorism. The four options provided are China, Japan, Russia, and the USA.

Option 1, China, is the correct answer. India and China have cooperated on a number of military and anti-terrorism training exercises, with `Hand-in-Hand 2007` being one of them.

Option 2, Japan, is not correct. Although India and Japan have been involved in bilateral military exercises, they did not collaborate for this particular session.

Option 3, Russia, isn`t accurate either. Despite the fact that Russia and India have a history of military cooperation and joint exercises, `Hand-in-Hand 2007` didn`t involve Russia.

Lastly, option 4, the USA, is not the correct answer. While India and the USA do have military cooperations, `Hand-in-Hand 2007` was not one such occasion.

Therefore, the correct answer remains Option 1, China.