Reason (R): The expedition sent by Shahjahan to the Middle East was a marvelous success.
Assertion (A) is true. Dara Shikoh, the eldest son of Emperor Shahjahan, was indeed appointed to lead military expeditions to Balkh, Badakhshan, and Qandahar. These campaigns were undertaken by Shahjahan between 1647 and 1652 CE as part of his policy to reclaim ancestral Mughal territories in Central Asia and to secure the northwestern frontier against the Safavids.
Reason (R) is false. The expeditions sent by Shahjahan to these regions were not a "marvelous success."
Therefore, Assertion (A) is true, but Reason (R) is false.
Options 1, 2, and 4 are incorrect because Reason (R) is factually false. The expeditions to Balkh, Badakhshan, and Qandahar during Shahjahan's reign are historically documented as failures, marked by substantial expenditure, military setbacks, and the permanent loss of Qandahar. Consequently, any option that states R is true or that R provides a correct explanation for A cannot be correct.