Question: Most modern air defence systems are fairly mobile. Even the larger systems tend to be mounted on trailers and are designed to be fairly quickly broken down or set up. In the past, this was not always the case. Early missile systems were cumbersome and required much infrastructure; many could not be moved at all. With the diversification of air defence there has been much more emphasis on mobility. Most modern systems are usually either self-propelled (i.e. guns or missiles are mounted on a truck or tracked chassis) or easily towed. Even systems that consist of many components (transporter/erector/launchers, radars, command posts etc.) benefit from being mounted on a fleet of vehicles. In general, a fixed system can be identified, attacked and destroyed whereas a mobile system can show up in places where it is not expected. Soviet systems especially concentrate on mobility, after the lessons learnt in the Vietnam war between the USA and Vietnam. For more information on this part of the conflict, see SA-2 Guideline.
Try to answer this question if possible: Contemporary air defence systems are usually what?
Answer: mobile
Question: Matte solder is usually fused to provide a better bonding surface or stripped to bare copper. Treatments, such as benzimidazolethiol, prevent surface oxidation of bare copper. The places to which components will be mounted are typically plated, because untreated bare copper oxidizes quickly, and therefore is not readily solderable. Traditionally, any exposed copper was coated with solder by hot air solder levelling (HASL). The HASL finish prevents oxidation from the underlying copper, thereby guaranteeing a solderable surface. This solder was a tin-lead alloy, however new solder compounds are now used to achieve compliance with the RoHS directive in the EU and US, which restricts the use of lead. One of these lead-free compounds is SN100CL, made up of 99.3% tin, 0.7% copper, 0.05% nickel, and a nominal of 60ppm germanium.
Try to answer this question if possible: What alloy can no longer be used in HASL because of restrictions on the use of one of its metal components?
Answer: tin-lead
Question: This contrasts with the presidential system, in which the president (or equivalent) is both the head of state and the head of the government. In some presidential or semi-presidential systems, such as those of France, Russia or South Korea, the prime minister is an official generally appointed by the president but usually approved by the legislature and responsible for carrying out the directives of the president and managing the civil service. The head of government of the People's Republic of China is referred to as the Premier of the State Council and the premier of the Republic of China (Taiwan) is also appointed by the president, but requires no approval by the legislature.
Try to answer this question if possible: What is another name for the Republic of China?
Answer: Taiwan
Question: Railroads have been an important method of transportation in Montana since the 1880s. Historically, the state was traversed by the main lines of three east-west transcontinental routes: the Milwaukee Road, the Great Northern, and the Northern Pacific. Today, the BNSF Railway is the state's largest railroad, its main transcontinental route incorporating the former Great Northern main line across the state. Montana RailLink, a privately held Class II railroad, operates former Northern Pacific trackage in western Montana.
Try to answer this question if possible: How long have railroads been important since in Montana
Answer:
1880s