In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

The idea that the transmission began in the 2nd or 1st century is what?, Context: The Silk Road transmission of Buddhism to China is most commonly thought to have started in the late 2nd or the 1st century CE, though the literary sources are all open to question.[note 41] The first documented translation efforts by foreign Buddhist monks in China were in the 2nd century CE, probably as a consequence of the expansion of the Kushan Empire into the Chinese territory of the Tarim Basin.
commonly thought