What is the remainder of W=3^19 when divided by 10? Choose the correct choice from the following choices:  A) 0  B) 1  C) 5  D) 7  E) 9

Rationale: "i looked for patterns : ^ 2 - units digit 9 ^ 3 - units digit 7 ^ 4 - units digit 1 ^ 5 - units digit 3 hence , we can see that when raised to a power which is multiple of 4 , the units digit is 1 , and when to an even power not multiple of 4 , the units digit is 9 and we can then see : ^ 16 - units digit 1 , or ^ 18 - units digit 9 and ^ 19 - units digit 7 therefore , w = when divided by 10 , the remainder must be 7 . d"
Answer: D