These bonds are collateralized securities with first claims in the event of bankruptcy. These bonds are not backed by any physical collateral. They are backed by the reputation and creditworthiness of the issuing company. These bonds are considered the riskiest of all corporate bonds and thus offer the highest interest rates.

Subordinated debentures - Ranks the lowest in terms of priority with regards to claim on assets, is the riskiest of all. Higher the risk, higher would be the return offered on the bond.

Debentures - These bonds are those which are not backed by any collateral. Issued by both corporations as well as governments, debentures are backed only by the general creditworthiness and reputation of the issuer.

Senior Mortgage Bonds - 'Senior' means they rank high in terms of claims on assets and 'Mortgage' implies they are backed by collateral.

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.'

urban company reports the following information regarding its production cost: units produced 37,000 units direct labor $ 30 per unit direct materials $ 35 per unit variable overhead $ 237,000 in total fixed overhead $ 127,000 in total