every must move TM is equivalent to a basic TM$.$Why?

a$.$ a must$-$move TM can be seen as a basic TM that happens not to have any transition that uses the "stay" option

b$.$ give a basic TM$,$ we can convert it into must$-$move Tm by replacing every stay$-$transition by two transitions, a transition that moves left followed by a transition that move right. That left move transition writes what the stay transition does, and the right move transition ends up in the same target state as the stay$-$transition