The correct answer is (d), Kevlar.
Kevlar is a strong, lightweight synthetic fiber that is used in a variety of applications, including bulletproof vests, helmets, and body armor. It is made from a long, chain-like molecule called para-aramid, which is very resistant to stretching and breaking. Kevlar is also very heat-resistant, making it ideal for use in bulletproof vests and other applications where it may be exposed to high temperatures.
Orlon is a type of acrylic fiber that is used in a variety of applications, including clothing, carpets, and insulation. It is a relatively soft and lightweight fiber that is not particularly strong or heat-resistant.
Nomex is a type of flame-resistant, heat-resistant, and chemical-resistant synthetic fiber that is used in a variety of applications, including clothing, gloves, and gaskets. It is a relatively strong and durable fiber that is not particularly resistant to bullets.
Lexan is a type of polycarbonate resin that is used in a variety of applications, including bulletproof glass, eyewear, and medical devices. It is a strong and lightweight material that is resistant to impact and chemicals. However, it is not as strong as Kevlar and is not typically used in bulletproof vests or other applications where high levels of protection are required.