Which of the following releases thromboplastin?

Blood cells -

Which of the following blood corpuscles secrete serotonin?
$I$. Basophils $\quad$ $II$. Eosinophils
$III$. Thrombocytes $\quad$ $IV$. Lymphocytes
$V$. Monocytes
Select the correct option from the following:

Which of the following statements is most appropriate regarding blood components and the transport of respiratory gases?

The ratio of $RBC$ to $WBC$ in man is (in $: 1$)

Which of the following structures is absent in fresh refrigerated blood plasma?