Questions

The persons with 'O' blood group do not have antigens in the red corpuscles. So that blood will not cause agglutination of corpuscles if mixed with any type of blood. So group 'O' persons are called universal donors.

The Von Hippel Award, the Materials Research Society's highest honor, recognizes those qualities most prized by materials scientists and engineers—brilliance and originality of intellect, combined with vision that transcends the boundaries of conventional scientific disciplines. The Von Hippel Award is named after Arthur von Hippel (1898-2003), who was a pioneer in the study of dielectrics, semiconductors, ferromagnetics and ferroelectrics.

Eminent Scientist and Bharat Ratna Prof C.N.R. Rao was awarded 2017 Von Hippel Award. He is first Indian and first Asian to win this honour. The award will be presented to Prof Rao for his interdisciplinary contributions to development of novel functional materials, including nanomaterials, graphene, superconductivity, 2D materials and colossal magnetoresistance at Boston in November 2017.

Our solution:

Toss the coin twice.
Let TH, HT and TT correspond to the three choices.
And if you get HH, just repeat (so it takes 8/3 tosses on average).


BIASED COIN

If the coin was biased, TH and HT would occur with equal probability.
So you could assign THHT, HTTH and THTH to the three choices, with other 4-toss outcomes rejected.
Or you could assign HTT, THT and TTH to the three choices, with other 3-toss outcomes rejected.

Allotropes are the different physical forms of an element. Here in the given options, diamond and graphite are the pair of allotropes of carbon.

Some more examples are Molecular oxygen and ozone are pair of allotropes, Black and red phosphorous are also pairs of allotropes.