OPTION AND SERIES D+ PREFERENCE SHARES PURCHASE AGREEMENT by and among LINKDOC TECHNOLOGY LIMITED, LINKDOC TECHNOLOGY HK LIMITED (零氪科技香港有限公司), LING KE INFORMATION TECHNOLOGY (BEIJING) CO., LTD. (零氪信息技术 (北京)有限公司), LING KE INVESTMENT (TIANJIN) CO., LTD....