Given a sentence, fill out the missing word with a 'no' or a number (between zero and ten). You should write the numbers with english alphabet, like: four instead of 4.

Q: Biological islands are of ____ general types, geographical and ecological.

A: two
****
Q: Pyrimidines contain ____ ring and purines contain two rings.

A: one
****
Q: Cortical amplitudes range from less than ____ up to seven or more microvolts.

A:
one
****