Which sentence features a shift in tense?
a. she is breaking the plates she is carrying.
b. grammar has always been the secret to good writing.
c. he bought a car two weeks ago, and then he goes and buys a motorcycle last week!
d. the live broadcast will last until this evening, and then the station will return to its former programming.

What is the mass of the same rock on the earth

(a) assume the equation x = at^3 + bt describes the motion of a particular object, with x having the dimension of length and t having the dimension of time. determine the dimensions of the constants a and b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.) (b) determine the dimensions of the derivative dx/dt = 3at^2 + b. (use the following as necessary: l and t, where l is the unit of length and t is the unit of time.)

An ionic compound can conduct electricity when a it is dissolved in water b its crystals are ground into powder c it is in solid form d it is heated to just below its melting point