Neco 2018 Geography Question 6

A field geologist collected three rock samples from different geological settings in Nigeria. The observations recorded for each sample are as follows: **Sample A** – Collected from the basement complex in the north‑central region. It is hard, coarse‑grained, shows foliation, and reacts weakly to dilute hydrochloric acid. **Sample B** – Collected from the Niger Delta sedimentary basin. It is soft, fine‑grained, feels gritty, contains visible shell fragments, and effervesces vigorously when a few drops of dilute hydrochloric acid are applied. **Sample C** – Collected from the volcanic plateau of the Jos Plateau. It is dense, fine‑grained, dark‑coloured, magnetic, and contains phenocrysts of feldspar. Answer the following questions: