The answer is D: green triangle.

The rule
The pattern repeats every 3 things: green triangle, green triangle, green star. Then it starts again from the beginning.
The pattern as Python code
Here is a tiny Python program that follows the same rule. Type it into IDLE and run it to print the whole pattern, including the answer.
pattern = ["green triangle", "green triangle", "green star"]
for position in range(8):
print(position + 1, pattern[position % len(pattern)])
When you run it, Python prints:
1 green triangle 2 green triangle 3 green star 4 green triangle 5 green triangle 6 green star 7 green triangle 8 green triangle
Pixel says: Try changing a number in the code and run it again. Can you make the pattern go on for 20 steps? Meow!