ZAO Picture is a specialist company that deals in works of art. It acquired three paintings signed by a famous artist and decided to make these available for sale.The company sent letters to Nikolai, Peter and Svetlana stating the following:‘ZAO Picture is prepared to offer you an exclusive bargain. You have the opportunity to purchase a signed painting (full description given) by the famous artist Chaikin for 500.000 roubles. In order to secure your purchase please reply, enclosing full payment, by 13.00 hours on 1 February 2008’.Nikolai replied to the letter and sent full payment for the painting, but his reply did not reach ZAO Picture until 3 February 2008. Peter’s response was to send a remittance of 450.000 roubles, with a letter stating that he was prepared to purchase the painting but as a valued customer expected a discount of 10%. Svetlana did not reply, but the general director of ZAO Picture was certain that as an enthusiastic art collector she would wish to accept the offer and sent her a painting with an invoice for 500.000 roubles.Required:

(a) Explain whether the letters sent by ZAO Picture to the three clients were offers which, if accepted, formed the basis of binding contracts. (4 marks)

霍乱疫苗的接种途径为（）

A.皮下注射

B.皮内注射

C.肌内注射

D.口服

E.肌内或皮下注射