Why does a $99$mTc generator need to be shipped once a week to hospitals?

Not much of the original material remains after one week.

Not much of the daughter material remains after one week.

The activity of the original material becomes increasingly dangerous after one week.

The activity of the daughter material becomes increasingly dangerous after one week.

Correct: Your answer is correct.

$($b$)$

What is the activity $($in Bq$)$ of a $1011-$Bq $99$mTc generator source $8$ days after it was produced?

Bq

$($c$)$

If the activity is $0\mathrm{.}7501011$ Bq on Monday morning when it arrives, what will be the activity $($in Bq$)$ at the same time on Friday morning, the last day of the working week?

Bq