Problem: A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electrification has many advantages but requires significant capital expenditure. Selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to the revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas; some electric locomotives can switch to different supply voltages to allow flexibility in operation.
How do some locomotives function in order to be more flexible in operation?
The answer is the following: can switch to different supply voltages

Problem: The forests play a vital role in harbouring more than 45,000 floral and 81,000 faunal species of which 5150 floral and 1837 faunal species are endemic. Plant and animal species confined to a specific geographical area are called endemic species. In reserved forests, rights to activities like hunting and grazing are sometimes given to communities living on the fringes of the forest, who sustain their livelihood partially or wholly from forest resources or products. The unclassed forests covers 6.4 percent of the total forest area and they are marked by the following characteristics:
How many endemic faunal species do forests harbor?
The answer is the following: 1837

Problem: In the groups Z/nZ introduced above, the element 1 is primitive, so these groups are cyclic. Indeed, each element is expressible as a sum all of whose terms are 1. Any cyclic group with n elements is isomorphic to this group. A second example for cyclic groups is the group of n-th complex roots of unity, given by complex numbers z satisfying zn = 1. These numbers can be visualized as the vertices on a regular n-gon, as shown in blue at the right for n = 6. The group operation is multiplication of complex numbers. In the picture, multiplying with z corresponds to a counter-clockwise rotation by 60. Using some field theory, the group Fp can be shown to be cyclic: for example, if p = 5, 3 is a generator since 31 = 3, 32 = 9 4, 33 2, and 34 1.
What group is isomorphic to cyclic groups?
The answer is the following: Any cyclic group with n elements

Problem: In Charleston, the African American population increased as freedmen moved from rural areas to the major city: from 17,000 in 1860 to over 27,000 in 1880. Historian Eric Foner noted that blacks were glad to be relieved of the many regulations of slavery and to operate outside of white surveillance. Among other changes, most blacks quickly left the Southern Baptist Church, setting up their own black Baptist congregations or joining new African Methodist Episcopal Church and AME Zion churches, both independent black denominations first established in the North. Freedmen "acquired dogs, guns, and liquor (all barred to them under slavery), and refused to yield the sidewalks to whites".
Black left which religious denomination is great numbers after slavery?
The answer is the following:
Southern Baptist Church