The Hang Seng index dropped more than 4%, sliding below 20,000 to the lowest level since 2015… … as the Hang Seng China Enterprises Index closed down 7.2% on Monday, the biggest drop since November 2008. Meanwhile, the Hang Sang Tech Index tumbled 11% in its worst decline since the gauge was launched in July 2020, wiping out $2.1 trillion in value since a year-earlier peak, after the southern city of Shenzhen, a key tech hub near Hong Kong, was placed into lockdown to contain rising Covid-19 infections. The broader Hang Seng Index lost 5%. The US-traded Golden Dragon China...