What are the values of r and a1 for

? r = 0.45; a1 = 3 r = 0.45; a1 = 8 r = 8; a1 = 0.45 r = 8; a1 = 3

a1 or just a as it is in the equations is just the initial term of the sequence. In this case a1=1

r is the common ratio which is that constant ratio found by dividing any term by the term preceding it ...

In this case r=3/1=9/3=27/9=etc=3

So a1=1 and r=3, C. is your answer.