12. Which of the following lists are ordered from greatest to least? Select all the correct answers. A B 4.0times 10^-7, 2.0times 10^2, 3.0times 10^6, 5.0times 10^12 3.0times 10^7, 3.0times 10^6, 3.0times 10^2, 3.0times 10^-7 D 1.8times 10^9, 1.5times 10^5, 1.4times 10^-5, 1.9times 10^-8

To determine which lists are ordered from greatest to least, we need to compare the values in each list.

Let's analyze each option:

A: $$4.0\times 10^{-7},\quad 2.0\times 10^{2},\quad 3.0\times 10^{6},\quad 5.0\times 10^{12}$$
- $$4.0\times 10^{-7}$$ is the smallest value.
- $$2.0\times 10^{2}$$ is larger than $$4.0\times 10^{-7}$$ but smaller than the other values.
- $$3.0\times 10^{6}$$ is larger than $$2.0\times 10^{2}$$ but smaller than $$5.0\times 10^{12}$$ .
- $$5.0\times 10^{12}$$ is the largest value.

B: $$3.0\times 10^{7},\quad 3.0\times 10^{6},\quad 3.0\times 10^{2},\quad 3.0\times 10^{-7}$$
- $$3.0\times 10^{-7}$$ is the smallest value.
- $$3.0\times 10^{2}$$ is larger than $$3.0\times 10^{-7}$$ but smaller than the other values.
- $$3.0\times 10^{6}$$ is larger than $$3.0\times 10^{2}$$ but smaller than $$3.0\times 10^{7}$$ .
- $$3.0\times 10^{7}$$ is the largest value.

D: $$1.8\times 10^{9},\quad 1.5\times 10^{5},\quad 1.4\times 10^{-5},\quad 1.9\times 10^{-8}$$
- $$1.9\times 10^{-8}$$ is the smallest value.
- $$1.4\times 10^{-5}$$ is larger than $$1.9\times 10^{-8}$$ but smaller than the other values.
- $$1.5\times 10^{5}$$ is larger than $$1.4\times 10^{-5}$$ but smaller than $$1.8\times 10^{9}$$ .
- $$1.8\times 10^{9}$$ is the largest value.

Based on the analysis, the correct answers are:
A
B
D