The abbreviations for a tetragram, a nanosecond and a kiloliter are as follows:
Tg ,ns and kl.
Nanosecond is *10-9.
One teragram is ten raised to the power of 9 and one kiloliter is equivalent to one thousand liters.
D: All the variables are controlled except one.
It's some change in the conditions around the organism, which the organism can detect and respond to. A change in temperature, more light, or something physically poking the organism are examples.