uniting能用作unite的名词吗?

A.uniting B getting united 答案选 B 为什么啊 ?请大家帮帮忙
----------at beijing,together with all his family,was what he strongly wished for during the last leg of life
A.uniting B getting united 答案选 B 为什么啊 ?请大家帮帮忙

英语翻译
Couplings
A coupling is a mechanicl device for uniting or connecting parts of a mechanical system.This lesson concerns itself with those couplings which are used on machine shafts for the purpose of transmitting torque,Couplings may be employed for a permanent or semi-permanent connection between shafts,or for disconnection of machine components to permit one member to run while the other is stationary.
Commercial shafts are limited in length by manufacturing and shipping requirements so that it is necessary to join sections of long transmission shafts with couplings.Couplings are also required to connect the shaft of a driving machine to a separately built driven unit.Permanent couplings are referred to simply as couplings,while those which may be readily engaged to transmit power,or disengaged when desired,usually are called clutches.
Rigid couplings are permanent couplings which by virtue of their construction have essentially no degree of angular,axial,or rotational flexibility,they must be used with conllinear shafts.
The flange coupling shown in Figure 2-3 is perhaps the most common coupling.It has the advantage of simplicity and low cost,but the connected shafts must be accurately aligned to avoid severe bending stress and excessive wear in the bearings.The length of the hub is determined by the length of the key required,and the hub diameter is approximately twice the bore.The thickness of the flange is determined by the permissible bearing pressure on the bolts.Although usually not critical,the shearing stress on the cylindrical area where the flange joins the hub should be checked.
A collar coupling,shown in Figure 2-4,consists of a cylindrical collar pressed over the ends of the two collinear shafts being connected,approximately one-half of the collar connecting each shaft.Usually one or more radial pins completely through each shaft and the collar,or setscrews,may be used to ensure that there is no undesired radial moment.A variation of the collar coupling results if a cylindrical part of one shaft fits concentrically into female bored portion in the second shaft and pins,setscrews,or other suitable fasteners are used.
Upon occasion it is desired that couplings be able to accommodate reasonable amounts of axial angularity between shafts,a small amount of eccentricity between parallel shafts,or axial moment of shafts during use.Flexible couplings may be employed for any or all of these cases.In addition,torsionally flexible couplings may be employed to adsorb some of the torque in the shaft,or to permit large amounts of torsionally flexibility as in fluid couplings or torque converters.

the interlocking rings symbolize the uniting of all five continents particip这句话有哪些语法 知识点