It is often difficult to get measures of anxiety during competition of interacting sport teams (e. g., soccer, basketball). Another way to get some information about anxiety states during competition is to use:.a. physiological measures like heart rate.
b. retrospective measures.
c. prospective measure.
d. brain waves.
e. none of these.

b) Retrospective measures

Explanation:

Retrospective measures is the approach in which past information and study is used for collecting samples and starting research about same topic.This helps in easy conduction of research with less amount of time.

According to question, anxiety related information in competition of sport team can be known through retrospective measure as it will provide the past data of anxiety states occurring in sports competition.

Other options are incorrect because prospective measure, physiological approach and brain waves are not used for knowing information through past studies.Thus, the correct option is option(b)

this doesn't support enough information to answer the question.

i am pretty sure it is d.