People who are learning a foreign language think in their mother tongue (literally: when they think). The reason is that they cannot think coherently in the target language.
(d).
変化を遂げない経営は当然効率が悪くなります。なぜならば顧客も競合他社も常に変化しているからです。
Management that doesn't change will become ineffective, as a matter of course. The reason is that both customers and competitors are always changing.