I have an exercise related to verb forms / tenses. I have solved 9/10 questions easily, just the question below makes me confused:
Choose the correct form of verbs to fill in each blank.
Singapore housewife invents useful device
A useful device for getting rid of cockroaches has just been invented by a housewife. The device is called ‘Stop-Roach’ and will soon be on sale in department store and large shops.
‘Stop-Roach’ consists of a hollow cylinder and movable valve. It is placed in any drain or opening where there are cockroaches. Cockroaches trying to enter the house through the drain will find it impossible to get through the device.
‘Stop-Roach’ has been subjected to thorough tests by the Environment Ministry and the invention has now been patented. It has been found completely foolproof against invasions of cockroaches from drains and sewers. It _____ that ‘Stop-Roach’ will be on sale very soon for under ten dollars.
B. is expected
C. has expected
D. has been expected
The book's answer key is B (is expected). However, I don't know why the author doesn't choose option D (has been expected). I think the present perfect in option D can be used for something (be expected) that started in the past and continues in the present, so option D is also a correct answer for this question.
Is my understanding correct in this case?