The correct options are
C He fought a war against the Chalukyas and lost.
D He established control over a large part of northern India during his rule.
Harsha was not the eldest son of his father, but became king of Thanesar after both his father and elder brother died. His brother-in-law, the ruler of Kannauj, was killed by the ruler of Bengal, Sasanka. Harsha took over the kingdom of Kannauj, and then led an army against the ruler of Bengal. Although he was successful in the east, and conquered both Magadha and Bengal, he was not as successful elsewhere. He tried to cross the Narmada to march into the Deccan, but was stopped by a ruler belonging to the Chalukya dynasty, Pulakeshin II.