The Apple USB-C Digital AV Multiport Adapter is retailing for S$98.
This adapter extends a single USB-C port and adds an additional three more ports: HDMI, USB-A (normal USB) and USB-C.
You can use the HDMI port to connect to full HD (1920×1080) displays at 60Hz or 4K (3840×2160) displays at 30Hz.
According to Apple, this adapter is not compatible with the G-Tech G-DRIVE mobile USB 3.0 Hard Drive.
Personally, I find this adapter very expensive, you might as well get a USB-C Hub from Satechi instead.