Answer:
A dam that could allow fish to still pass through is a fishway/fish pass its a "fish ladder" that is structured on or around artificial or natural barriers to allow for fishes natural migration and the movement for potamodromous species.
Answer:
Pioneer species are hardy species which are the first to colonize previously biodiverse steady-state ecosystems. Some lichens grow on rocks without soil, so may be among the first form of life. The example includes bacteria, fungi, and lichens.
Answer:
Option A, Neither the researchers nor the study participants know who is receiving the drug and who is receiving the placebo.
Explanation:
In a double blind test, both the researcher and research participants are unaware of the exercise in a medical test . During the research active medication is given to some of the research participants making sure that researcher is unaware of that while observing all the participants. However, at the end of the experiment ,both the researcher and research participants get to know who has received the treatment.
Hence, option A is correct
