Polymers

Step 1: Osmium ( ) is a transition metal belonging to group 8 of the periodic table.
Step 2: Transition metals can exhibit oxidation states up to their group number.
Step 3: Osmium shows its highest oxidation state in compounds such as osmium tetroxide ( ).
Step 4: In , oxygen has an oxidation state of .
Step 5: To balance the charge, osmium must have an oxidation state of .

Step 1: Recall the structure of natural rubber and gutta-percha.
Natural rubber is \emph{cis}- -polyisoprene (i.e., -configuration).
Gutta-percha is \emph{trans}- -polyisoprene (i.e., -configuration).
Step 2: Relate configuration to physical properties.
-configuration (cis) → coiled chains → elastic and amorphous
-configuration (trans) → linear chains → highly crystalline and non-elastic Since gutta-percha is described as highly crystalline and non-elastic, it must have the trans ( ) configuration throughout.
Step 3: Match with the given options. Only option (A) correctly states that gutta-percha consists of
Hence, the correct answer is

Step 1: Recall what vinegar is. Vinegar is an aqueous solution obtained by the fermentation of alcohol. Step 2: Identify the major acid present. During fermentation: Vinegar typically contains about of acetic acid. Step 3: Analyze the options.

(A) Acetic acid — main constituent ✔
(B) Ascorbic acid — vitamin C
(C) Citric acid — found in citrus fruits
(D) Tartaric acid — found in grapes and tamarind
Step 4: Final conclusion. The main constituent of vinegar is acetic acid.