Even though Jack has failed many times in his experiment, he holds a belief________he will succeedone day if he carries on with it. [ ]

Which book is much better quality?[ ]

__in the 1800s and first mass-produced in Germany, the harmonicawas designed to play simple folk tunes.

How about the book you are reading?— Good indeed.It______ many problems we have come across in our study.[ ]

errible accident is underinvestigation—Actually, quicker action _____ thoseworkers trapped in the mine