Step 1: Understand the Act.
The Vernacular Press Act of 1878 was made to control Indian-language newspapers that criticised the British.
Step 2: Identify the Viceroy.
This Act was passed during the rule of Lord Lytton (1876-1880).
Step 3: Lytton's record.
He is also linked to the Arms Act of 1878 and the grand Delhi Durbar of 1877. His rule was unpopular.
Step 4: Rule out others.
Lord Ripon later repealed this Act in 1882. Lord Curzon (Bengal Partition) and Lord Dalhousie (Doctrine of Lapse) came at different times.
Step 5: Conclude.
The Act was passed under Lord Lytton.
Answer: Lord Lytton