The waltham system
a. employed whole families to work in textile mills.
b. employed young women in their late teens and early twenties.
c. employed young children, who often worked 10-12 hours per day.
d. was considered a disreputable form of employment for women.

Option A                

Explanation:

The Waltham-Lowell method was a labor and manufacturing paradigm implemented in the U.s during the growth of the textile industry, especially in New England, in the broader context of the initial 19th century rapid growth of the Industrialisation.

The program utilized regional labor, sometimes linked to as mill girls, who went from small towns to the fresh textile facilities to make more money than they might at home to live an educated life in "the town." Their lives were very structured-they lived in boarding houses for the corporation and were carried to stringent hours and a value system.

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.'