A single set of chromosomes is found in

(i) Secondary oocyte

(ii) Spermatogonium

(iii) Primary spermatocyte 

(iv) Secondary Spermatocyte

(v) Spermatid

Let's find out the number of chromosome in each of the following- 

i. Secondary oocyte - Haploid or contains a single set of chromosome

ii. Spermatogonium - Diploid cells, each contains 46 chromosome (23 pairs) 

iii. Primary spermatocyte -  Diploid because they produced by mitosis and have 46 chromosome.

iv. Secondary spermatocyte - Haploid because each primary spermatocytes goes through the first meiotic division to produce two secondary spermatocytes each with 23 chromosome. 

v. Spermatid - Haploid male gametid results from division of secondary spermatocyte. 

Hence, germinal cell, secondary spermatocyte and spermatid contains only one set of chromosome or haploid in nature.