Hey,

Every term which is written inside the sin is dimensionless, thus:

Bx= M^0 L^0 T^0

which means

B= M^0 L^-1 T^0

Lt= M^0 L^0 T^0

C=M^0 L^0 T^-1

D=M^0 L^0 T^0

A=M^0 L^1 T^0

Therefore,

the dimensional formula of ABCD  is

=(L^1 L^-1 T^-1)*(M^0 L^0 T^0) = M^0 L^0 T^-1

which is the required answer.

I hope this helps.

All the best!