Al-Biruni (A) with III. Caste system: Al-Biruni, a Persian scholar, extensively studied Indian culture and society during his visit in the 11th century. His works include insights into the caste system.

Ibn Battuta (B) with IV. Coconut and Paan: Ibn Battuta, a Moroccan traveler, explored India in the 14th century. His observations might have included details about local customs, including the use of coconut and paan.

Abdur Razzaq (C) with I. Kerala as a strange nation: Abdur Razzaq, a Persian ambassador, visited the Vijayanagara Empire in the 15th century. His descriptions might have included perceptions of Kerala as a unique or "strange" nation.

Pelsaert (D) with II. Widespread poverty: Francisco Pelsaert, a Dutch traveler, wrote about his experiences during the 17th century, which included observations on the economic conditions, potentially highlighting widespread poverty.

So, the correct option is [3].