Bullet proof helmets are made from:
A. Lexan
B. Saran
C. Glyptal
D. Thiokol

Hint: As we know that, bullet proof helmets are the bullet resistance masks. The material used in Bullet proof should be very tough and its strength should be very high.

Step by step answer: The bullet proof helmets are made up of the Lexan. Lexan is a ballistic resistant plastic. Other ballistic resistant plastics can be used for this purpose. Lexan is mainly used for making military aircraft canopies. Actually, Lexan is a thermoplastic polymer having carbonate groups in their chemical structure. The reason why Lexan is used for bullet resistance masks is its strength and toughness. Also, they can be easily moulded, worked and thermoformed. The monomer of this polymer is bisphenol A. Lexan is thus a polycarbonate resin thermoplastic with transparent and clear surface. Lexan is also used for making race car windows, windshields, DVDs, CDs, etc.
Saran is a thin plastic film which is generally used for wrapping food materials. It is also used for first aid dressing in case of burns. The chemical name of Saran is Polyvinylidene Chloride (PVDC). It is a copolymer which is hydrophilic in nature.
Glyptal also known as alkyl resin is a condensation polymer of ethylene glycol and phthalic acid. It is a polyester used for manufacturing lacquers and paints.
Thiokol is a polymer produced from the reaction of 2-chloroethanol, formaldehyde and sodium polysulphide. It is mainly used for making rubber gaskets.

Hence, option (A) Lexan, is the correct option.

Note: Thus, Lexan is the substance used for making bullet proof helmets. Lexan is a polycarbonate resin thermoplastic with glass-like clear and transparent surface. Its toughness, strength and quality to get easily moulded and work out are utilised for making the bullet proof masks. It is also used in making military aircraft canopies.