1.______a seven-second delay between transmission of the sig

1.______a seven-second delay between transmission of the signal and when it can be heard on computer
A.It is B.There is C.It has been D.There has been
2.You _________tell him.He is fully aware of the danger.
A.mustn't B.haven't to C,don't have to D.can;t
3.Hence the expansion cidtionary definitions descends into progessive generality,____a weaker and weaker semantic relationship with the original word.
A.displaying B.displayed C,to diaplay D.to be diaplayed