Identify the technique of Bengal School paintings of 19th century?

The correct answer is Option (3) → Wash technique

In the 19th century, the Bengal School of painting is known for its use of the wash technique, which is a combination of Japanese watercolor, European transparent watercolor, and Indian tempera.

Journey’s End: Made by Abanindranath Tagore (1871–1951) in 1913, this painting is in watercolour. Abanindranath Tagore was seen as a father figure of nationalist and modernism of art in India. He revived certain aspects of Indian and oriental traditions of paintings in terms of themes, style and techniques, and invented the wash painting technique. The wash technique yields a soft, misty and impressionistic landscape. This quality of hazy and atmospheric effects of the wash are utilised to be suggestive or evocative of an end of a life.

Note: There appears to be a discrepancy in the question. The wash technique is primarily associated with the Bengal School, which developed in the early 20th century, not strictly the 19th century as mentioned. However, based on NCERT, the correct technique linked to the Bengal School is the wash technique.