Final answer:
Option (c), Implementing an infant industry tariff may lead to inefficiency and lack of competition as protectionist policies can extend indefinitely, hampering the industry's growth and competitiveness.
Step-by-step explanation:
A problem encountered when implementing an "infant industry" tariff is that it may lead to inefficiency and lack of competition. The theory behind supporting infant industries is providing temporary protection to help these industries grow and become competitive internationally.
However, the intended short-term assistance may harden into long-term protection, preventing these industries from achieving the necessary efficiency and competitive edge due to the lack of market pressures. Furthermore, the protectionist policies often persist longer than planned and tend to benefit established industries with political power, undermining the objective of nurturing new, vibrant competitors.