When the All India Trade Union Congress was founded in 1920, Lala Lajpat Rai was elected as its president.

Option 1: C.R. Das was not elected as the president of the All India Trade Union Congress in 1920.

Option 2: Lala Lajpat Rai is the correct answer. He was indeed elected as the president of the All India Trade Union Congress in 1920.

Option 3: N.M. Joshi was not elected as the president of the All India Trade Union Congress in 1920.

Option 4: V.V. Giri was not elected as the president of the All India Trade Union Congress in 1920.

Therefore, the correct answer is option 2, Lala Lajpat Rai.