Read the passage given below and complete the statements that follow using the…

Read the passage given below and complete the statements that follow using the help of given options.

Passage :
Today diesel engines can be seen in use all over the world. In size they range all the way from small, single-cylinder versions of 3 kW driving water pumps to mammoth multi-cylinder marine engines.
Buses, lorries, locomotives, tractors, bulldozers, mobile cranes and ships are powered by big diesel engines. Stationary uses of the engine include generating sets and pump sets, etc. For a rugged, powerful and mobile source of energy the diesel engine is preferred. It is heavier than a corresponding petrol engine but far lower in fuel consumption. Heavy transportation and road construction could not have been possible without the diesel engine.

Even in the case of passenger vehicles where petrol engines reign supreme so far due to lighter weight and smoother running, diesel engines are making gradual inroads. We may see more of diesel-powered cars in future due to the superiority of the diesel engine in fuel economy and performance. Although the petrol engine once cost much more than the diesel engine, it is now the other way round, as diesel engine combustion is more complex.

Much of this we owe to Dr. Rudolf Diesel, who could not enjoy the fruits of his labour. This genius in engineering was unbelievably inept in money management and lost much of what he earned. He was deeply disturbed at the rapid worsening of relations between the French and the Germans. The portents of the coming holocaust, the First World War, were too evident to be ignored. On 29 September, 1913, Dr. Diesel took the ferry to Britain on business and disappeared during the voyage; presumably he got drowned in the sea.

Question : The word ‘portents’ as used in the last paragraph means —