Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Experimental group 1 | Experimental group 2 | Variable that is manipulated in experiment |
| --- | --- | --- |
| plants near a sunny window | plants in a dark room | light |
| plants at high altitude | plants at low altitude | air |
| plants watered weekly | plants watered monthly | water |
| plants in sand | plants in garden soil | soil |
Question:
"In Experimental group 2, plants were watered monthly. Experimental group 1 included _______." Select the correct choice to answer the question or fill in the blank.
Choices:
(A) plants in sand
(B) plants at a high altitude
(C) plants watered weekly
(D) plants near a sunny window
Answer:
(C) plants watered weekly