What factor is most likely responsible for the long-term trend in europe's population growth? a. shorter life excpectancyb. fewer birthsc. higher infant mortalityd. births that exceed replacemtn-level fertility

The correct answer is option B, that is, fewer births.  

Aging of Europe also called greying of Europe, refers to a demographic process in Europe featured by a reduction in fertility, higher life expectancy, and a decrease in mortality rate among the European populations. Higher life expectancy and low birth rates donate to the modification of Europe's population pyramid shape.  

The most substantial modification is the transformation towards a much older population composition, leading to a reduction in the ratio of the working age, while the number of the retired population enhances.  

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]