[Voters in Africa’s most populous country and largest economy cast ballots for a new leader in the Feb. 25 Nigerian general elections. Here are answers to some essential questions about the vote]

Trade between the world’s two biggest economies has ballooned in recent decades, bringing significant benefits but also perils that have led to calls to rethink the relationship.

A significant proportion of China’s population claims to follow a religion. However, the government continues to toughen oversight, increase persecution of some religions, and attempt to co-opt state…