WASHINGTON — In their first conversation in seven months, President Biden spoke on Thursday with President Xi Jinping of China, expressing concern over China’s cyberactivities while arguing that the leaders of the world’s two largest economies could set aside their differences to work together on climate change.The call amounted to a break in what experts have called one of the lowest points in the relationship between the two countries in decades. It was only the second time that the leaders have spoken since Mr. Biden’s inauguration; the lack of communication is a measure of the rising tensions …
