The reason that the producers of wood pulp have often forward integrated into the production of paper is:

you don't if you paid you paid. it's like if i bought a computer and used it then i say idon't want it anymore so im gonna return it. you can't. unlkess you have your reciept

ans.

heterothermic organisms include those organisms that can switch between homeothermic (having body temperature higher than environment) and poikilothermic (having variation in internal body temperature) strategies.

some migratory birds show heterothermy as they decrease their metabolic rate during cold nights to keep their body temperature low. drop in metabolic rate allows increase in production efficiency of birds that reduces the internal body temperature to make it equal to external cold temperature during cold nights.

thus, the correct answer is 'birds allow their temperature drop in order to increase their production efficiency.'