Which mammal below lays tough leathery eggs? A) bear (placental) B) duck-billed platypus (monotreme) C) kangaroo (marsupial) D) bat (placental)

the answer to your question is B) Monotreme.

Explanation:

most mammals do not lay eggs, they give birth. But, monotreme mammals including the duck-billed platypus do in fact lay shelled eggs.

b) mutualism

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when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.